TreeMap练习：对学生对象进行按年龄升序排序

最新推荐文章于 2024-08-07 23:42:58 发布

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本文介绍了一种使用Java实现的学生对象按年龄升序排序的方法，并展示了如何利用TreeMap结合自定义比较器进行排序的过程。通过具体代码实例，演示了如何创建学生对象，以及如何在TreeMap中存储这些对象并按姓名和年龄进行排序。

【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 StuNameComparator implements Comparator<Student>
{
	public int compare(Student s1,Student s2){
		int num=s1.getName().compareTo(s2.getName());
		if (num==0)
		{
			return new Integer(s1.getAge()).compareTo(new Integer(s2.getAge()));
		}
		return num;
	}
}
class  MapDemo2
{
	public static void main(String[] args) 
	{
		TreeMap<Student,String> hm=new TreeMap<>(new StuNameComparator());
		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",27),"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......beijing
				lisi01::27......lijiang
				lisi02::29......taiwan
				lisi03::26......xianggang
				lisi04::23......shanghai
			*/
		}
	}
}

【输出】：