练习1

package QM_Fx;

import java.util.ArrayList;

public class test{
    public static void main(String[] args) {
        //1.创建一个集合
        ArrayList<String> list=new ArrayList<>();
        //2.添加元素
        list.add("点赞了吗");
        list.add("投币了吗");
        list.add("收藏了吗");
        list.add("转发了吗");
        System.out.print("[");
        //3.遍历元素
        for (int i = 0; i < list.size(); i++) {
            if(i==list.size()-1) {
                System.out.print(list.get(i));
            }else{
                System.out.print(list.get(i)+",");
            }

        }
        System.out.println("]");
        

    }

}
/*
[点赞了吗,投币了吗,收藏了吗,转发了吗]

 */

练习2

用集合储存数组要将数据进行包装类

代码

import java.util.ArrayList;

public class test{
    public static void main(String[] args) {
        //1.创建一个集合
        ArrayList<Integer> list=new ArrayList<>();
        //2.添加元素
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        System.out.print("[");
        //3.遍历元素
        for (int i = 0; i < list.size(); i++) {
            if(i==list.size()-1) {
                System.out.print(list.get(i));
            }else{
                System.out.print(list.get(i)+",");
            }

        }
        System.out.println("]");


    }

}
/*
[1,2,3,4]

 */

char得用单引号

import java.util.ArrayList;

public class test{
    public static void main(String[] args) {
        //1.创建一个集合
        ArrayList<Character> list=new ArrayList<>();
        //2.添加元素
        list.add('a');
        list.add('a');
        list.add('a');
        list.add('a');
        System.out.print("[");
        //3.遍历元素
        for (int i = 0; i < list.size(); i++) {
            if(i==list.size()-1) {
                System.out.print(list.get(i));
            }else{
                System.out.print(list.get(i)+",");
            }

        }
        System.out.println("]");


    }

}
/*
[a,a,a,a]

 */