1、實體類實現comparable介面，重寫compareTo方法

package io;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Student implements Comparable<Student>{
	
	private String name;
	private int age;
	private Date birthDay;
	
	
	
	public Student(String name, int age, String birthDay) {
		super();
		this.name = name;
		this.age = age;
		
		DateFormat ds=new SimpleDateFormat("yyyy-MM-dd");
		try {
			this.birthDay = ds.parse(birthDay);
		} catch (ParseException e) {
			e.printStackTrace();
		};
	}
	
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Date getBirthDay() {
		return birthDay;
	}
	public void setBirthDay(Date birthDay) {
		this.birthDay = birthDay;
	}
	
	//按名字降序 按生日升序
	@Override
	public int compareTo(Student o) {
		int result=0;
		result=-this.name.compareTo(o.name);
		if(result==0){
			result=this.birthDay.compareTo(o.birthDay);
		}
		return result;
	}


	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + ", birthDay=" + birthDay + "]";
	}
	

}
 

package io;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class App {

	public static void main(String[] args) {
		
		List<Student> list=new ArrayList<Student>();
		list.add(new Student("張三", 20, "1987-10-5"));
		list.add(new Student("王五", 22, "1986-10-5"));
		list.add(new Student("趙六", 25, "1988-10-5"));
		list.add(new Student("王七", 19, "1980-10-5"));
		Collections.sort(list);
		for(Student s:list){
			System.out.println(s);
		}
	}
}
 

2、建立新的業務類實現comparator介面，重寫compare方法。

package io;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Student {
	
	private String name;
	private int age;
	private Date birthDay;
	
	
	
	public Student(String name, int age, String birthDay) {
		super();
		this.name = name;
		this.age = age;
		
		DateFormat ds=new SimpleDateFormat("yyyy-MM-dd");
		try {
			this.birthDay = ds.parse(birthDay);
		} catch (ParseException e) {
			e.printStackTrace();
		};
	}
	
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Date getBirthDay() {
		return birthDay;
	}
	public void setBirthDay(Date birthDay) {
		this.birthDay = birthDay;
	}
	


	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + ", birthDay=" + birthDay + "]";
	}
	

}
 

package io;

import java.util.Comparator;

public class BirthdayComp implements Comparator<Student>{


	@Override
	public int compare(Student o1, Student o2) {
	
		return o1.getBirthDay().compareTo(o2.getBirthDay());
	}

}

package io;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class App {

	public static void main(String[] args) {
		
		List<Student> list=new ArrayList<Student>();
		list.add(new Student("張三", 20, "1987-10-5"));
		list.add(new Student("王五", 22, "1986-10-5"));
		list.add(new Student("趙六", 25, "1988-10-5"));
		list.add(new Student("王七", 19, "1980-10-5"));
		Collections.sort(list, new BirthdayComp());
		for(Student s:list){
			System.out.println(s);
		}
	}
}