javaSE（11）（集合迭代器与比较器）
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迭代器接口：package zz.itheima.comparator;public interface Iterator { public boolean hasNext(); public int next();}package zz.itheima.comparator;public interface Interable { public Iterator iterator();}ArrList类：package zz.itheima.comparator;public class ArrList { //此类就当成ArrayList private int[] num; private int index; public ArrList() { num = new int[10]; index = 0; } public void add(int o){ for (int i = 0; i < num.length; i++) { if (num[i]==0) {//数组的默认值为0； num[i] = o; break; } } } public int get(int index){ return num[index]; } public int size(){ return num.length; } public Iterator iterator(){ return new Iterator0(); } class Iterator0 implements Iterator{ @Override public boolean hasNext() { if (index<num.length) { return true; }else { return false; } } @Override public int next() { return num[index++]; } }}TestArrList ：package zz.itheima.comparator;public class TestArrList { public static void main(String[] args) { ArrList al = new ArrList(); al.add(10); al.add(18); System.out.println(al.get(0)); for (int i = 0; i < al.size(); i++) { System.out.println(al.get(i)); } System.out.println("**************************"); Iterator it = al.iterator(); while (it.hasNext()) { System.out.println(it.next()); } }}运行结果：10101800000000**************************101800000000beans类：package zz.itheima.comparator;public class Book implements Comparable<Book>{ private String name; private int price; public Book(String name, int price) { super(); this.name = name; this.price = price; } public Book() { super(); // TODO Auto-generated constructor stub } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } @Override public String toString() { return "Book [name=" + name + ", price=" + price + "]"; } //此方法必须从写 @Override public int compareTo(Book o) { int res = this.getName().compareTo(o.getName()); if (res==0) {//名字相等 return this.getPrice()-o.getPrice();//名字相等的话比较价格 }else { return res;//名字不相等话就直接返回int型数字，正数是大于，负数是小于 } }}package zz.itheima.comparator;public class Stu implements Comparable<Stu> { private String name; private int age; public Stu(String name, int age) { super(); this.name = name; this.age = age; } public Stu() { super(); // TODO Auto-generated constructor stub } @Override public String toString() { return "Stu [name=" + name + ", age=" + age + "]"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public int compareTo(Stu o) {// int res = this.getName().compareTo(o.getName());// if (res==0) {//名字相等的情况下比较年龄// return this.getAge() - o.getAge();// }else {// return res;// } int res=this.age-o.getAge(); if(res==0) { return this.name.compareTo(o.getName()); } else { return res; } }}TestStu类：package zz.itheima.comparator;import java.util.TreeSet;public class TestStu { public static void main(String[] args) { TreeSet<Stu> hs = new TreeSet<Stu>(); hs.add(new Stu("张一", 80)); hs.add(new Stu("张三", 10)); hs.add(new Stu("李四", 16)); System.out.println(hs); }}运行结果：[Stu [name=张三, age=10], Stu [name=李四, age=16], Stu [name=张一, age=80]]TestSort类：package zz.itheima.comparator;import java.util.Arrays;public class TestSort { public static void main(String[] args) { // 回顾一下Arrays.sort()方法的作用，并思考一下如果数组存储的是自定义类型的数据，会怎么排序？ String[] str = {"bcd","aca","abc"}; Arrays.sort(str); for (int i = 0; i < str.length; i++) { System.out.println(str[i]); } System.out.println("**********************"); //如果数组存储的是自定的类型的数据 Book[] book = new Book[3]; book[0] = new Book("b", 2); book[1]=new Book("c", 3); book[2]=new Book("a", 1); Arrays.sort(book); for (int i = 0; i < book.length; i++) { System.out.println(book[i]); } }}运行结果：abcacabcd**********************Book [name=a, price=1]Book [name=b, price=2]Book [name=c, price=3]泛型：package zz.itheima.comparator;import java.util.ArrayList;public class GenericType<T>{ private T o; public void setO(T o){ this.o = o; } public T geto(){ return o; } GenericType<Book> fx = new GenericType<Book>(); ArrayList<Book> al = new ArrayList<Book>();}BookComparator1类：package zz.itheima.comparator;import java.util.Comparator;//自定义了一个专门用于图书类的比较器(第一种算法)public class BookComparator1 implements Comparator<Book> { @Override public int compare(Book o1, Book o2) { int res = o1.getName().compareTo(o2.getName()); if (res==0) { return o1.getPrice() - o2.getPrice(); }else { return res; } }}BookComparator2类：package zz.itheima.comparator;import java.util.Comparator;//自定义了一个专门用于图书类的比较器(第二种算法)public class BookComparator2 implements Comparator<Book>{ @Override public int compare(Book o1, Book o2) { int res = o1.getPrice() - o2.getPrice(); if (res==0) { return o1.getName().compareTo(o2.getName()); }else { return res; } }}TestComparator类：package zz.itheima.comparator;import java.util.TreeSet;public class TestComparator { public static void main(String[] args) { /*自定义图书类不实现任何接口 创建一个该接口的实现类实现排序算法(按书名) 在一个TreeSet(有参构造)中存储几个图书对象，并输出该TreeSet进行测试 如果书名一样，价格不同，会怎样？*/ /*java.util.Comparator接口 int compare(T o1,T o2) 自定义一个类实现该接口并重写该方法实现排序算法 TreeSet类有一个public TreeSet(Comparator<T> comp)构造方法可以指定排序算法类*/ TreeSet<Book> ts=new TreeSet<Book>(new BookComparator2()); ts.add(new Book("abc", 10)); ts.add(new Book("aa", 1)); ts.add(new Book("aa", 10)); System.out.println(ts); }}运行结果：[Book [name=aa, price=1], Book [name=aa, price=10], Book [name=abc, price=10]]TestBinarySerach类：package zz.itheima.comparator;import java.util.ArrayList;import java.util.Collections;public class TestBinarySerach { public static void main(String[] args) { ArrayList<Book> al2=new ArrayList<Book>(); al2.add(new Book("accc", 21)); al2.add(new Book("aaa", 10)); al2.add(new Book("abc", 11)); al2.add(new Book("ddd", 12)); al2.add(new Book("eee", 13)); Collections.sort(al2, new BookComparator2()); System.out.println(al2); System.out.println("*********************"); int res = Collections.binarySearch(al2,new Book("accc", 21), new BookComparator2()); System.out.println(res); }}运行结果：[Book [name=aaa, price=10], Book [name=abc, price=11], Book [name=ddd, price=12], Book [name=eee, price=13], Book [name=accc, price=21]]*********************4TestCollections类：package zz.itheima.comparator;import java.util.ArrayList;import java.util.Collections;public class TestCollections { public static void main(String[] args) {// public static <T> int binarySearch(List list, T key) ArrayList<String> al1 = new ArrayList(); al1.add("aaa");al1.add("bbb");al1.add("ccc"); String key = "bbdfg"; int res1 = Collections.binarySearch(al1, key); System.out.println(res1); System.out.println("******************");// public static <T> int binarySearch(List list, T key, Comparator c) ArrayList<Book> al2=new ArrayList<Book>(); al2.add(new Book("accc", 12)); al2.add(new Book("aaa", 10)); al2.add(new Book("bbb", 11)); al2.add(new Book("ddd", 11)); al2.add(new Book("eee", 11)); System.out.println(al2); Collections.sort(al2,new BookComparator2()); int res2=Collections.binarySearch(al2, new Book("accc", 12),new BookComparator2()); System.out.println(res2); System.out.println("**************************");// public static <T > T max(Collection<T> coll) ArrayList<String> al3=new ArrayList<String>(); al3.add("aaa"); al3.add("abc"); al3.add("cdf"); al3.add("add"); System.out.println(Collections.max(al3)); System.out.println("*********************");// public static <T> T max(Collection<T> coll, Comparator<T> comp) ArrayList<Book> al4=new ArrayList<Book>(); al4.add(new Book("ccc", 10)); al4.add(new Book("aaa", 12)); al4.add(new Book("bbb", 11)); System.out.println(Collections.max(al4, new BookComparator2())); System.out.println("*******************");// public static <T> T min(Collection<T> coll)// public static <T> T min(Collection<T> coll, Comparator<T> comp)// public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) ArrayList<String> al5=new ArrayList<String>(); al5.add("aaa"); al5.add("abc"); al5.add("cdf"); al5.add("abc"); al5.add("add"); al5.add("abc"); //Collections.replaceAll(al5, "abc", "hello"); System.out.println(al5);// public static void reverse(List<T> list) Collections.reverse(al5); System.out.println(al5);// public static <T> void sort(List<T> list) Collections.sort(al5); System.out.println(al5);// public static <T> void sort(List<T> list, Comparator<T> c) Collections.sort(al4, new BookComparator2()); System.out.println(al4);// public static void shuffle(List<?> list) Collections.shuffle(al5); System.out.println(al5);//重新洗牌 }}运行结果：-3******************[Book [name=accc, price=12], Book [name=aaa, price=10], Book [name=bbb, price=11], Book [name=ddd, price=11], Book [name=eee, price=11]]4**************************cdf*********************Book [name=aaa, price=12]*******************[aaa, abc, cdf, abc, add, abc][abc, add, abc, cdf, abc, aaa][aaa, abc, abc, abc, add, cdf][Book [name=ccc, price=10], Book [name=bbb, price=11], Book [name=aaa, price=12]][cdf, abc, aaa, abc, add, abc] 0 0
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