2021-05-07集合框架1.Array List

package edu.xcdp;

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

public class Demo01 {
    public static void main(String[] args) {
        String [] str = new String[] {"1e21" , "12q" ,"aqwdfqw"};
        str[0] = "111";
        str[1] = "222";
        str[2] = "333";
        // 删除位置为1的元素
        str[1] = str[2];
        str[2] = null ;


        ArrayList<String> list = new ArrayList<>(); //数组列表 底层是数组
        list.add("111");
        list.add("222");
        list.add("333");
        list.add("444");
        list.add("555");   //增加
        System.out.println(list);
        list.remove(1); //删除
        list.remove("444");
        System.out.println(list);
        list.set(2 , "55555");  //修改
        System.out.println(list);
        // 查询
        for (String l : list) {
            System.out.println(l + "\t");
        }
        System.out.println(list);
        for (int i =0; i < list.size(); i++){
            System.out.println(list.get(i)+"\t");
        }
    }
}