JAVA | 57

Collection 是集合操作的接口，Collections 是集合操作的工具类，可以进行 List，Set，Map 集合的操作。

import java.util.ArrayList;import java.util.Collections;import java.util.List;class Book{    private String title;    private int price;    public Book(String title, int price){        this.title = title;        this.price = price;    }    @Override    public String toString() {        return this.title + " " + this.price;    }    @Override    public boolean equals(Object obj) {        if(obj == this){            return true;        }        if(obj == null){            return false;        }        if(!(obj instanceof Book)){            return false;        }        Book book = (Book) obj;        if(book.title.equals(this.title) && book.price == this.price){            return true;        }        return false;    }}public class Main {    public static void main(String[] args) throws Exception{        // 设置了泛型，从而保证集合中所有的数据类型都一致        List <Book> list = new ArrayList <Book> ();        Collections.addAll(list,new Book("java",100),new Book("c",89),new Book("c++",100),new Book("python",100),new Book("python",100));        System.out.println(list);        Collections.reverse(list);        System.out.println(list);    }}