1.建立一個Student2 類

package com.test.collection;

public class Student2 {
	public static String school;
	private String stuName;
	private int age;
	private String major;
	public Student2(String stuName, int age, String major) {
		
		this.stuName = stuName;
		this.age = age;
		this.major = major;
	}
	public Student2() {
		
		// TODO Auto-generated constructor stub
	}
	public String getStuName() {
		return stuName;
	}
	public void setStuName(String stuName) {
		this.stuName = stuName;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getMajor() {
		return major;
	}
	public void setMajor(String major) {
		this.major = major;
	}
	@Override
	public String toString() {
		return "Student2 [stuName=" + stuName + ", age=" + age + ", major=" + major + "]";
	}
	public void sayHello() {
		System.out.println("大家好！我叫" + this.stuName + "，今年" + age + "歲了。");
	}
}
 

2.建立比較器----Student2Comparator類

package com.test.collection;

import java.util.Comparator;
//建立Student2Comparator類，並實現Comparator介面，限定比較的物件為Student2物件
public class Student2Comparator  implements Comparator<Student2>{
	@Override
	public int compare(Student2 o1, Student2 o2) {
		// 實現Comparator介面，必須重寫compare方法
		//重寫compare方法,來比較物件的年齡
		//如果被比較物件的年齡o1.age大於o2.age,返回1
		//如果被比較物件的年齡o1.age小於o2.age,返回-1
		//通過修改返回值，可以實現升序或降序排序
		if (o1.getAge()>o2.getAge()) {
			return 1;
		}else if (o1.getAge()<o2.getAge()) {
			return -1;
		}
		return 0;
	}

}
 

3.建立測試類Student2Test

package com.test.collection;

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



public class Student2Test {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		List<Student2> stuList =new ArrayList<Student2>();
		Student2 s1 = new Student2("張三",30,"軟體工程");
		Student2 s2 = new Student2("李四",19,"軟體工程");
		Student2 s3= new Student2("王五",40,"軟體工程");
		//把s1,s2,s3三個Student2例項，新增到stuList中
		stuList.add(s1);
		stuList.add(s2);
		stuList.add(s3);
		
		
		//使用foreach遍歷stuList，並呼叫stuList中每個物件的sayHello()方法
		System.out.println("排序前：");
		for (Student2 s : stuList) {
			s.sayHello();
		}
		
		
		
		//使用Collections.sort排序，兩個引數情況下--（List例項名，new一個比較器物件 ）
		//兩個引數情況下，Student2Comparator比較器類必須實現Comparator介面，必須重寫compare方法
		//通過重寫compare方法，修改返回值，可以實現升序或降序排序
		Collections.sort(stuList,new Student2Comparator());
		System.out.println("使用Comparator介面，升序排序後：");
		for (Student2 s : stuList) {
			s.sayHello();
		}
		
	}

}