在list集合中的添加、修改、删除和遍历元素

集合与数组相似，但他的长度是可变的

list集合继承了collection接口，list集合的实现类是ArrayList()。

如下：

package com.test;import java.util.ArrayList;// import the ArrayList packageimport java.util.List;// import the List packagepublic class Test {public List list;//declare List collectionTest(){this.list= new ArrayList();//Implementation of List collection}}

list集合中的元素是有序的，可重复的。

先定义一个Student类

package com.test;public class Student {public String m_name;public int m_id;public Student(int id,String name){this.m_name= name;this.m_id = id;}}

再定义一个类，里面包含main()方法来实现

然后在list集合中添加元素

package com.test;import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class Test {public List<Student> list;public Test(){this.list= new ArrayList<Student>();}//add to studentpublic void TestAdd(){Student stu = new Student(1,"小明");list.add(stu);//add studentStudent stu1= new Student(2,"小李");list.add(0, stu1);//Specify the location to add the studentStudent[] stu2= {new Student(3,"小陈"),new Student(4,"小周")};list.addAll(Arrays.asList(stu2));//Add a number of studentStudent[] stu3= {new Student(5,"小吴"),new Student(1,"小明")};list.addAll(2, Arrays.asList(stu3));//Specify the location to add a number of student}public static void main(String[] args) {Test test = new Test();test.TestAdd();}}

在list集合中遍历元素：

<pre name="code" class="java">

public void TestFor(){int size = list.size();//get the length of the listfor(int i=0; i<size; i++){Student stu = list.get(i);//get element of the listSystem.out.println("student: "+stu.m_id+":"+stu.m_name);}System.out.println();}//Using ForEach traversal elementspublic void TestForEach(){for(Student stu:list){//Get elements from the list to the Student objectSystem.out.println("student: "+stu.m_id+":"+stu.m_name);}System.out.println();}//Using iterator traversal elementpublic void TestIterator(){Iterator it = list.iterator();//Define iterator objectswhile(it.hasNext()){//Whether the judgment is emptyStudent stu = (Student)it.next();//Mandatory conversion of iterator object to the Student objectSystem.out.println("student: "+stu.m_id+":"+stu.m_name);}System.out.println();}public static void main(String[] args) {Test test = new Test();test.TestAdd();<span style="white-space:pre"></span>test.TestFor();<span style="white-space:pre"></span>test.TestForEach();<span style="white-space:pre"></span>test.TestIterator();}

result is：

student: 2:小李<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 2:小李<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 2:小李</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明</span><span style="font-family: Arial, Helvetica, sans-serif;"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明</span>student: 5:小吴<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 5:小吴<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 5:小吴</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明</span>student: 3:小陈<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 3:小陈<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 3:小陈</span>student: 4:小周<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周</span>

在list集合中修改元素：

<pre name="code" class="java">//modify elementpublic void TestModify(){list.set(3, new Student(6,"小张"));//Replace the element with the specified location in the list with the new elementthis.TestFor();}<pre name="code" class="java">public static void main(String[] args) {Test test = new Test();test.TestAdd();<span></span>test.TestFor();<span></span>test.TestModify();}

result is：

student: 2:小李<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 2:小李</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明</span>student: 5:小吴<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 5:小吴</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 6:小张</span>student: 3:小陈<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 3:小陈</span>student: 4:小周<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周</span>

在List集合中删除元素：

<pre name="code" class="java">//delete studentpublic void TestRemove(){list.remove(3);//Remove elements from the specified locationthis.TestFor();list.remove(list.get(0));//Direct delete elementthis.TestFor();Student[] stu = {(Student)list.get(1),(Student)list.get(2)};//get multiple elementslist.removeAll(Arrays.asList(stu));//delete multiple elementsthis.TestFor();}<pre name="code" class="java">public static void main(String[] args) {Test test = new Test();test.TestAdd();<span></span>test.TestFor();<span></span>test.TesRemove();}

result is：

student: 2:小李<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 2:小李<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 1:小明<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 5:小吴<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周</span>student: 5:小吴<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 5:小吴<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 3:小陈</span>student: 1:小明<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 3:小陈<span style="white-space:pre"></span></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周</span>student: 3:小陈<span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">student: 4:小周</span>student: 4:小周