在list集合中的添加、修改、删除和遍历元素_listutil 可以修改的list 加元素-优快云博客

本文介绍了Java编程中List集合的基本操作，包括如何添加元素、遍历元素、修改元素。重点讲解了ArrayList作为List集合实现类的使用，并通过示例代码展示了具体的操作步骤。

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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 package
import java.util.List;			// import the List package
public class Test {

	public List list;		//declare List collection
	
	Test(){
		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 student
	public void TestAdd(){
		Student stu = new Student(1,"小明");
		list.add(stu);						//add student
		Student stu1= new Student(2,"小李");
		list.add(0, stu1);					//Specify the location to add the student
		Student[] stu2= {new Student(3,"小陈"),new Student(4,"小周")};
		list.addAll(Arrays.asList(stu2));					//Add a number of student
		Student[] 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 list
	for(int i=0; i<size; i++){
		Student stu = list.get(i);		//get element of the list
		System.out.println("student: "+stu.m_id+":"+stu.m_name);
	}
	System.out.println();
}
//Using ForEach traversal elements
public void TestForEach(){
	for(Student stu:list){			//Get elements from the list to the Student object
		System.out.println("student: "+stu.m_id+":"+stu.m_name);
	}
	System.out.println();
}
//Using iterator traversal element
public void TestIterator(){
	Iterator it = list.iterator();			//Define iterator objects
	while(it.hasNext()){				//Whether the judgment is empty
		Student stu = (Student)it.next();	//Mandatory conversion of iterator object to the Student object
		System.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 element
public void TestModify(){
	list.set(3, new Student(6,"小张"));		//Replace the element with the specified location in the list with the new element
	this.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 student
public void TestRemove(){
	list.remove(3);				//Remove elements from the specified location
	this.TestFor();
	list.remove(list.get(0));		//Direct delete element
	this.TestFor();
	Student[] stu = {(Student)list.get(1),(Student)list.get(2)};	//get multiple elements
	list.removeAll(Arrays.asList(stu));				//delete multiple elements
	this.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