java 容器类之（4）map系列

Map：拥有将对象映射到另一对象的能力，这可以帮助我们解决很多编程问题。
标准Java类库包含了这几种基本实现：HashMap,LinkedHashMap,TreeMap,ConcurrentHashMap等。map通过将键值绑定，能方便我们通过键查询值，它的键组可以视为一个Set集合，因此不含重复的元素。

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Map<Student, Integer> map = new TreeMap<Student, Integer>();
        Student[] stu = new Student[5];
        stu[0]=new Student("wang",70);
        stu[1]=new Student("li", 80);
        stu[2]=new Student("zhang",70);
        stu[3]=new Student("zhao", 90);
        stu[4]=new Student("sun", 90);
        for(int i=0;i<5;i++){
            map.put(stu[i], i);
        }
        Set<Student> set = map.keySet();
        System.out.println(map);
        System.out.println(set);
    }
}

class Student implements Comparable<Student>{
    String name;
    int score;
    @Override
    public int compareTo(Student o) {
        // TODO Auto-generated method stub
        if(this.equals(o))
            return this.score-o.score;
        else
            return this.score>=o.score?1:-1;
    }

    public Student(String name,int score){
        this.name=name;
        this.score=score;
    }

    public String toString(){
        return name+" "+score;
    }

    public boolean equals(Object o){
        return o instanceof Student && this.name==((Student)o).name && this.score==((Student)o).score;
    }

    /*public int hashCode(){
        return score;
    }*/
}