黑马程序员--集合框架
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集合
定义:为了方便对多个对象的操作,就对对象进行存储,集合就是其中的一种方式
集合和数组的不同之处:
1,数组是固定长度的,集合是可变长度的
2,数组可以储存基本数据类型和引用型数据类型,集合只能存储引用数据类型
3,数组存储的元素必然是统一个数据类型,集合存储的对象是不同数据类型
数据结构:
数据结构就是容器中存储数据的方式,对于集合容器，有很多种。因为每一个容器的自身特点不同，其实原理在于每个容器的内部数据结构不同。
集合容器在不断向上抽取过程中。出现了集合体系。
集合框架结构图:
Collection接口
- add(E e);
- addAll (Colletion c) //将一个容器中所有元素添加到指定容器
- clear() //清空容器
- remove()
- removeAll()
- contains()
- size()
- retainAll() //取交集 ，a1中只会保留与a2 中存在的元素
toArray //返回包含Collection所有元素的对象数组
iterator //返回一个实现了iterator接口的对象，可以使用这个迭代器依次访问集合中的元素
- Iterator it = al.iterator() //创建一个关联al 的Iterater类对象，
- it.next() // 反复调用next方法，可以依次访问集合中的每一个元素，每查找一个元素，迭代器随之向前移动
- hasNext() //使用next方法前，必须调用hasNext确定是否到达集合尾，否则在集合尾调用next会抛出异常
- remove() //删除迭代器上一个访问的元素（next方法），迭代器指向集合中相连的两个元素之间，调用remove之前必须县调用next方法。
<code class="hljs r has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">Collection<<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span>> c= new Collection<<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span>>();Iterator<<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span>> it = c.iterator<<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span>>();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(it.hasNext()){ //也可以使用<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> each循环 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span>(<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span> elements: c){} <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">T</span> t = it.next();}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>List
- List 的特点，元素是有序的，且元素可以重复，因为该集合体系有索引
- Set 的特点 ，元素是无序的，而且集合中元素不可重复
List中常用的方法
- ListIterator listIterator //返回一个列表迭代器，以便访问列表中的元素
- void add(int i ,Object obj) //指定位置添加一个元素
- Object remove(int i) //删除指定位置元素，并返回这个元素
- Object get(int i) //获取指定位置元素
- Object set (int i ,Object obj) //用新元素取代给定位置的元素，并返回被取代的元素
- int indexOf(Object obj) // 返回指定元素在列表中第一次出现的位置，如果没有这样的元素返回-1；list集合特有的迭代器，ListIterator是Iterator的子接口
在迭代时，不可以使用集合对象的方法操作集合中的元素。因为会发生异常
只能用迭代器的方法操作，可以Iterator方法有限，
所以需要使用其子接口 ListIterator来满足操作需求- void add( Object obj) 在当前位置添加一个元素
- void set （Object obj) 用新元素取代next或者previous上次访问的元素。
- hasPrevious ()
- int nextIndex() //返回下一次调用next(）方法时，将返回的元素索引
* List的三个子类： * - ArrayList 底层使用数组数据结构 （查询速度很快，增添删除麻烦）线程不同步
- LinkedList 底层使用的是链表元素 增添元素容易，但不适合随机存储
- Vector 底层是数组数据结构 线程同步，被ArrayList取代
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">import java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span>.*class ListDemo{ public static void main(String[] args){ ArrayList a1 = ArrayList()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"1dsf"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"2dd"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"3da"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> sop(a1)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"tianjia"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> sop(a1)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.remove</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; </span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"change"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> Iterater it = a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.iterate</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; //使用迭代器</span> while(it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()){ sop(it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } //演示list迭代器(添加或者删除元素） <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/* while(it.hasNext()){ Object obj = it.next(); if(obj.equeal("changge")) //这里有集合和迭代器两种方法操作元素， it.remove(); //a1.add("jvav");迭代器调用next时，在调用集合的方法会产生并发访问，抛出异常 sop(obj); */</span> // 因为迭代器对象被返回时，只知道有三个元素，使用<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">add</span>添加一个元素，迭代器并不知道 //所以使用迭代器遍历时，只可以使用迭代器的方法操作元素,否则抛出concurrentmodificationException, ListIterator li = a1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.listIterator</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> while (li<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()){ Object obj = li<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> if(obj<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.equals</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"change"</span>) li<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"zaijiayige"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> li<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"fasdfa"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } } sop(a1）； }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li></ul>List的三个子类：
- ArrayList 底层使用数组数据结构 （查询速度很快，增添删除麻烦）线程不同步
- LinkedList 底层使用的是链表元素 增添元素容易，但不适合随机存储
- Vector 底层是数组数据结构 线程同步，被ArrayList取代
LinkedList
- LinkedList()
- LinkedList(Collection
<code class="hljs lasso has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> java<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>util<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">*</span>;class LinkedListDemo{ LinkdList <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">new</span> LinkedList(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>addFirst(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"java01"</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>addLast(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"java02"</span>); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//添加到尾</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>addFirst(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"java03"</span>); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//添加到头，</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">String</span> s1<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>getFirst(); <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">String</span> s2<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>getLast(); <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">String</span> s2<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>removeFirst() <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//取出第一个元素并删除，如果集合没有元素会抛出NoSuchElementException异常</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">While</span>(<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">!</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>isEmpty()){ sop(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>removeFirst()); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>pollFirst() <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//返回并移除第一个元素，如果没有元素返回null </span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>使用LinkedLisst模拟一个堆栈或者队列数据结构
<code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//模拟队列</span>import java.util.*;class Duilie{ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> LinkedList link; Duilie(){ link = LinkedList(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">addOne</span>(Object obj){ link.addFirst(obj); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">getOne</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">object</span> obj){ Link.removeLast(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//堆栈是removeFirst();</span> } } class DuilieTest{ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args){ Duilie dl=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Duilie(); dl.addOne(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"my01"</span>); dl.addOne(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"my01"</span>); dl.addOne(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"my01"</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(!dl.isEmpty()){ dl.getOne(); } } }</code><code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>取出ArrayList集合中的重合元素
<code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">class ArrayListTest{ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> main（String[] args){ ArrayList al = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayList(); al.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value01"</span>); al.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value02"</span>); al.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value03"</span>); al.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value01"</span>); sop(al); al = singleElement(al); sop(al); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/* Iteator it = al.iterator(); while (it.hasNext()){ sop(it.next()); } */</span> } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> List <span class="hljs-title" style="box-sizing: border-box;">singleElement</span>(ArrayList al){ ArrayList newAl = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayList(); Iterator it = al.iterator(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(it.hasNext()){ Object obj = it.next(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!newAl.contains(obj)) newAl.add(obj); } } }</code><code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>set
- 元素是无序的（存入和取出的顺序不一定一致）
- Set集合的功能和collection一致
- 常见的子类
- HashSet 底层数据结构是哈希表。、
- HashSet 如何保证元素的唯一性：通过元素的两个方法，hashCode和equals来完成
- 先判断HashCode值，如果HashCode值相同，再判断equals。原则先判断主要，后判断次要 - TreeSet 底层结构是二叉树
- HashSet 底层数据结构是哈希表。、
<code class="hljs actionscript has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Demo</span>{</span>}<span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">HashSetDemo</span>{</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> main(String[] args){ HashSet hs = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> HashSet(); hs.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value01"</span>); hs.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value02"</span>); hs.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value03"</span>); hs.add(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value01"</span>); Iterator it = hs.iterator(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//set集合取值只有一种方式 迭代器</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(it.hasNext()){ sop(it.next()); } }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>使用HashSet 存储对象，一般需要在类中重写 hashCode 和equals 方法使对象间可以相互比较拥有自然顺序
<code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//以类Person为例</span>class Person{ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String name; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> age; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">Person</span>(String name, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> age){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name= name; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.age = age; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">hashCode</span>(){ System.out.println(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"...hashcode"</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name.hashCode()+age } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">equals</span>(Object obj){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!(obj <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">instanceof</span> Person){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; Person p = (person)obj; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name.equals(p.name)&&<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.age==p.age; } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li></ul>TreeSet
- TreeSet
- 可以对Set集合中的元素进行排序，输出由小到大
- TreeSet底层数据结构是二叉树，保证元素唯一性的依据是compareTo方法return 0；
- TreeSet 排序的第一种方式，
- 让元素自身具有比较性，元素需要实现Comparable接口，覆盖conpareTo方法，叫做元素的自然顺序 - TreeSet排序的第二种方式
- 当元素自身不具备比较性时，这是就需要让集合自身具备比较性。 定义比较器 - 当两种方法都存在，以比较器为主
- 如何定义比较器
- 定义一个实现了Comparator接口的类，覆盖compare方法
<code class="hljs php has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//往TreeSet集合中存入自定义对象，并按照学生的年龄排序</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//当主要条件相同时，一定要判断次要条件。</span><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Sturdents</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Comparable</span>{</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//该接口强制使类具有比较性</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String name; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> int age; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Students(String name,int age){ this.name = name; this.age = age; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String getName(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> name; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> int getAge(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> age; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> int compareTo(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!obj <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">instanceof</span> Students()) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RuntimeException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"不是学生对象”); Students s = (Student)obj; if(this.age>s.age) return 1; if(this.age=s.age){ return this.name.compareTo(s.name); return -1; }}class TreeSetDemo{ public static void main(String[] args){ TreeSet ts = new TreeSet(); ts.add(new Studeng("</span>lisi<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">",14)); ts.add(new Studeng("</span>wang<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">",13)); //如果存入的对象不具有比较性，会抛出异常。 ts.add(new Studeng("</span>lee<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">",16)); ts.add(new Studeng("</span>lisi<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">",14)); Iterator it = ts.iterator(); while(it.hasNext()){ Studeng str= (Student)it.next(); System.out.println(str.getName()+str.getAge()); } } }</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li></ul><code class="hljs axapta has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//当元素自身不具有比较性，这是需要让容器自身具有比较性，定义个比较器，将比较器对象作为参数传递给TreeSet</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//集合的构造函数</span>import java.util.*<span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Sturdents</span> <span class="hljs-inheritance" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span></span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Comparable</span>{</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//该接口强制使类具有比较性</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String name; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> age; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Students(String name,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> age){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name = name; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.age = age; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String getName(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> name; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> getAge(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> age; }}<span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TreeSetDemo</span>{</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> main(String[] args){ TreeSet ts = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TreeSet(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyCompare()); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//传入自定义的构造器</span> ts.add(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Studeng(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"lisi"</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">14</span>)); ts.add(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Studeng(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wang"</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">13</span>)); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果存入的对象不具有比较性，会抛出异常。</span> ts.add(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Studeng(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"lee"</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">16</span>)); ts.add(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Studeng(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"lisi"</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">14</span>)); Iterator it = ts.iterator(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(it.hasNext()){ Studeng <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>= (Student)it.next(); System.out.println(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.getName()+<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.getAge()); } } } <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyComepare</span> <span class="hljs-inheritance" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span></span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Comparator</span>{</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> compare(Object o1,Object o2){ Students s1= (Students)o1; Students s2= (Students)o2; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> num = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> (s1.getName().compareTo(s2.getName()); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(num==<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(s1.getAge()>s2.getAge() ) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(s1.getAge()==s2.getAge()) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> num; } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li></ul>练习 ：按照字符串长度排序
字符串本身具有比较性，但不符合要求，这是需要定义比较器
<code class="hljs haskell has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">StrLenComparator</span> implements <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Comparator</span>{ public int compare<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Object</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">o1</span>,<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Object</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">o2</span>)</span>{ <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">String</span> s1 = <span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">String</span>)</span> o1; <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">String</span> s2 = <span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">String</span>)</span> o2; /* if<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">s1</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">lengh</span>()</span>>s2.length<span class="hljs-container" style="box-sizing: border-box;">()</span>) return 1; if<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">s1</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">lengh</span>()</span>==s2.length<span class="hljs-container" style="box-sizing: border-box;">()</span>) return 0;/* int num = new <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Integer</span><span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">s1</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">length</span>()</span>)compareTo<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">new</span> <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Integer</span>(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">s2</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">length</span>()</span>); if <span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">num</span>==0)</span> return s1.compareTo<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">s2</span>)</span>; return num;}</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>Map集合：该集合存储键值对，而且保证键的唯一
- 添加
- put(key,value); 返回V,存相同键时，新键代替旧键，并且返回旧键的值
- putAll(map)
- 删除
- remove(Object key)
- clear();
- 判断
- containKey()
- containValue()
- isEmpty()
获取
- get(Object key)
- size()
- values() //返回映射中包含值的Collection视图
Map集合的两种取出方式(map集合不需要迭代器，转换成set集合，通过迭代器运行，
- Set
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">import java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span>.*class MapDemo{ public static void main(String[] args){ Map<String,String> map = new HashMap<String,String><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"01"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"lee"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"02"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"liu"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"03"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wang"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.containsKey</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"01"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.remove</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"01"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; //根据键值删除元素</span> map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"02"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; //键值不存在返回空，可以用来判断是否存在</span> Colletion<String> coll=map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.values</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(coll)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> //获取map集合所有键的<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>集合， <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Set</span><String> keySet = map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.keySet</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> Iterator<String> it = keySet<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.itrator</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> while(it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()){ String key = it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> //根据键获取对应的值 String value = map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(key)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(key+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"..."</span>value)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Set</span><Map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Entry</span><String,String>> entrySet=map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.entrySet</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> Iterator<Map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Emtry</span><String,String>> it = entrySet<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.iterator</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> while(it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()){ Map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Entry</span><String,String> me = it<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> String key = me<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getKey</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> String value = me<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getValue</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(key+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"..."</span>value)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } } } </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li></ul>Collections 集合框架工具类
sort();
max();
binarySearch(list,”aaa”)
fill(list,”pp”); //将集合中的元素全部替换成指定元素
replaceAll(list,oldVaule,newValue);
reverse(list)
reverseOrder() //强行逆转了实现Comparable接口collection对象的自然排序
//强行逆转指定比较器的顺序
Arrays :用于操作数组的工具类
Collections.sort(list);
Collections.sort(list,new Comparator())
Collections.max(sort);
int index=Collections.binarySearch(list,”aaa”);
0 0
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