集合框架之Collection工具类

• 集合框架之Collections工具类

概念：集合工具类，定义了除了存取以外的集合常用方法

package com.oop.demo11;

import java.util.*;

/**
 * Collection工具类的使用
 */
public class Demo15 {
    public static void main(String[] args) {
        List<Integer> list = new ArrayList<>();
        list.add(20);
        list.add(5);
        list.add(12);
        list.add(30);
        list.add(6);
        //sort排序
        System.out.println("排序之前："+list);
        Collections.sort(list);
        System.out.println("排序之后："+list);
        //binarySearch
        int i=Collections.binarySearch(list,12);
        System.out.println(i);
        System.out.println("----复制----");
        List<Integer>dest=new ArrayList<>();
        for (int k=0;k<list.size();k++){
            dest.add(0);
        }
        Collections.copy(dest,list);
        System.out.println(dest.toString());
        System.out.println("----reverse反转----");
        Collections.reverse(list);
        System.out.println("反转之后："+list);
        System.out.println("----shuffle打乱----");
        Collections.shuffle(list);
        System.out.println("打乱之后："+list);
        System.out.println("----list转成数组----");
        Integer[] arr=list.toArray(new Integer[0]);
        System.out.println(arr.length);
        System.out.println(Arrays.toString(arr));
        System.out.println("----数组转成集合----");
        String [] names={"张三","李四","王五"};
        List<String> list2=Arrays.asList(names);
        System.out.println(list2);

    }
}