普通的增強for迴圈遍歷時移出元素報錯

package com.fridge.controller.cms;

import java.util.ArrayList;
import java.util.List;

/**
 * @program: mythicalanimals
 * @description: 集合遍歷時移出元素demo
 * @author: TheEternity Zhang
 * @create: 2020-06-08 14:27
 */
public class ListIteratorDemo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add("abc");
        list.add("abe");
        list.add("hgf");
        list.add("zzx");
        for (String str: list) {
            if(str.contains("a")){
                list.remove(str);
            }else{
                System.out.println(str);
            }
        }
        System.out.println("集合的數量:"+list.size());
    }
}
 

丟擲ConcurrentModificationException異常

Connected to the target VM, address: '127.0.0.1:62068', transport: 'socket'
Exception in thread "main" java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)
	at java.util.ArrayList$Itr.next(ArrayList.java:859)
	at com.fridge.controller.cms.ListIteratorDemo.main(ListIteratorDemo.java:19)
Disconnected from the target VM, address: '127.0.0.1:62068', transport: 'socket'
 

使用Iterator在遍歷時移出元素

package com.fridge.controller.cms;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * @program: mythicalanimals
 * @description: 集合遍歷時移出元素demo
 * @author: TheEternity Zhang
 * @create: 2020-06-08 14:27
 */
public class ListIteratorDemo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add("abc");
        list.add("abe");
        list.add("hgf");
        list.add("zzx");
        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()){
            String str = iterator.next();
            if(str.contains("a")){
                iterator.remove();
            }else{
                System.out.println(str);
            }
        }
        System.out.println("集合的數量:"+list.size());
    }
}

 

結果

hgf
zzx
集合的數量:2