🧨🧨🧨🧨Collections集合工具类

public class demoCollection {
    public static void main(String[] args) {
        ArrayList<String> list=new ArrayList<>();
        Collections.addAll(list,"a","b","c","d");
        System.out.println(list);//[a, b, c, d]

        Collections.shuffle(list);//打乱顺序：打乱集合顺序
        System.out.println(list);
    }
}

public class demoColl {

    public static void main(String[] args) {
        ArrayList<Integer> list=new ArrayList<>();
        list.add(1);
        list.add(5);
        list.add(3);
        
        Collections.sort(list);
        System.out.println(list);//[1,3,5]


        ArrayList<String> list1=new ArrayList<>();
        list1.add("b");
        list1.add("z");
        list1.add("a");
        Collections.sort(list1);
        System.out.println(list1);//[a, b, z]
    }
}

public class dmeoSort {
    public static void main(String[] args) {
        ArrayList<Integer>  list=new ArrayList<>();
        list.add(5);
        list.add(1);
        list.add(2);
        System.out.println(list);

      Collections.sort(list,new Comparator<Integer>(){
            //重写比较的规则
          @Override
          public int compare(Integer o1,Integer o2){
              return o2-o1;//降序[5, 2, 1]
          //return o1-o2;//升序//[1, 2, 5]
          }
        });
        System.out.println(list);

    }
}