colleations工具类

package WangGang01;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.stream.Collector;

public class Dome07 {
    public static void main(String[] args) {
        //Collection不支持创建对象，因为构造器私有化了
        //Collections cols =new Collections();
        //里面的属性和方法都是被static修饰，我们可以直接用类名，去调用即可
        //常用方法
        //addAll
        ArrayList<String> strings = new ArrayList<>();
        strings.add("bb");
        strings.add("aa");
        strings.add("cc");
        Collections.addAll(strings,"dd","ee","ff");
        Collections.addAll(strings,new String[]{"66","55","SD"});
        System.out.println(strings);
        Collections.sort(strings);//sort提供了一个升序的排列
        System.out.println(strings);
        //copy替换
        ArrayList<String> strings1 = new ArrayList<>();
        Collections.addAll(strings1,new String[]{"5","6"});
        Collections.copy(strings,strings1);
        System.out.println(strings);
        System.out.println(strings1);
        //fill填充
        Collections.fill(strings,"666");
        System.out.println(strings);
    }
}