Comparable和Comparator之对象比较-优快云博客

本文详细介绍了如何在Java中创建实体类并实现对象的比较和排序功能，通过使用Comparator和Comparable接口，展示了如何根据年龄属性对Student对象进行升序或降序排列。

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创建一个实体类：

package cn.com.comparator;

public class Students 
{
	private String name;
	private int age;
	
	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;
	}
}

Comparator实现对象比较

package cn.com.comparator;

import java.util.Comparator;

public class StudentComparator implements Comparator
{
	public int compare(Object o1, Object o2)
	{
		int result=0;
		if(o1!=null&&o2!=null&&o1 instanceof Students && o2 instanceof Students)
		{
		Students stu1=(Students)o1;
		Students stu2=(Students)o2;
	        result=stu1.getAge()-stu2.getAge();
		}
		else
		{
			RuntimeException e=new RuntimeException("对象不存在或者不是Students的类型");
			throw e;
		}
		return result;
	}

	

}
Comparable实现对象比较：

package cn.com.comparator;

public class StudentComparable implements Comparable
{
    private String name;
    private int age;

	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 int compareTo(Object o)
	{
		int result=0;
		if(o!=null&&o instanceof StudentComparable)
		{
			StudentComparable student=(StudentComparable)o;
			result=this.age-student.age;
			
		}
		else
		{
			RuntimeException e=new RuntimeException("对象不能为空或者不是StudentComparable类型");
			throw e;
		}
		return result;
	}

}

编写测试类：

package cn.com.comparator;

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

public class StudentTest
{
	public static void test()
	{
		List<Students> stuList=new ArrayList<Students>();
		//List<StudentComparable> stuList2=new ArrayList<StudentComparable>();
		
		Random ran=new Random();
		for(int i=0;i<10;i++)
		{
			Students stu=new Students();
			stu.setName("name:"+i);
			stu.setAge(ran.nextInt(35));
			stuList.add(stu);
			
		}
		Comparator stuComparator=new StudentComparator();
		Collections.sort(stuList,stuComparator);
		//Collections.reverse(stuList);反转顺序，逆转输出
		
		//Comparable stuComparable=new StudentComparable();
		
		
		//Collections.sort(stuList2);
		for(Students stu:stuList)
		{
			System.out.println(stu.getName()+": "+stu.getAge());
		}
		
	}

	public static void main(String[] args)
	{
	
		test();

	}

}