HashMap练习：对学生对象进行按年龄升序排序

叁歲伎倆 2021-09-19 08:26 369阅读 0赞

【需求】：对学生对象进行按年龄升序排序

学生Student(name,age)     地址String

【代码】：

/*
    需求：
    学生Student(name,age)	 地址String
    
    */
    import java.util.*;
    class Student implements Comparable<Student>
    {
    	private String name;
    	private int age;
    	Student(String name,int age){
    		this.age=age;
    		this.name=name;
    	}
    	public String getName(){
    		return name;
    	}
    	public int getAge(){
    		return age;
    	}
    	public int compareTo(Student s){
    		int num=new Integer(this.age).compareTo(new Integer(s.age));
    		if (num==0)
    		{
    			return this.name.compareTo(s.name);
    		}
    		return num;
    	}
    
    	public int hashCode(){
    		return name.hashCode()+age*12;
    	}
    	public boolean equals(Object obj){
    		if(!(obj instanceof Student)){
    			throw new RuntimeException("不是学生对象");
    		}
    		Student s=(Student)obj;
    		return this.name.equals(s.name)&&this.age==s.age;
    	}
    	public String toString(){
    		return name+"::"+age;
    	
    	}
    }
    class  MapDemo
    {
    	public static void main(String[] args) 
    	{
    		HashMap<Student,String> hm=new HashMap<>();
    		hm.put(new Student("lisi01",23),"beijing");
    		hm.put(new Student("lisi02",29),"taiwan");
    		hm.put(new Student("lisi03",26),"xianggang");
    		hm.put(new Student("lisi04",23),"shanghai");
    		hm.put(new Student("lisi01",23),"beijing");
    		hm.put(new Student("lisi01",23),"lijiang");
    
    		//keySet取出
    		Set<Student> keySet=hm.keySet();
    		Iterator<Student> it=keySet.iterator();
    		while(it.hasNext()){
    			Student s=it.next();
    			String addr=hm.get(s);
    			System.out.println(s+"......"+addr);
    			/*
    				lisi01::23......lijiang
    				lisi04::23......shanghai
    				lisi03::26......xianggang
    				lisi02::29......taiwan	
    			*/
    		}
    	}
    }

【输出】：

![20190509211554570.png][]

[20190509211554570.png]: /images/20210811/cf0ac735b9194cbfa206143807a586a7.png