Java 两种比较器的区别:Comparable 与 Comparator

Comparable

java.lang.comparable :
是在一个类定义的时候默认实现好的接口, 里面存在有一个 compareTo() 方法

实现案例

package com.cwq.beyond;

import java.text.SimpleDateFormat;
import java.util.Arrays;

class Person implements Comparable<Person>{

	private String name;
	private int age;
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	
	@Override
	public int compareTo(Person o) {
		if (this.age > o.age) {
			return 1;
		}else if (this.age < o.age) {
			return -1;
		}else {
			return 0;
		}
	}
	
}

public class TestDemo {
	public static void main(String[] args) throws Exception {

		Person p[] = new Person[] {
				new Person("张三", 20) ,
				new Person("张四", 18) ,
				new Person("王五", 19) ,
		};
		Arrays.sort(p);
		System.out.println(Arrays.toString(p));
		
	}

}

Comparator

java.util.comparator:
是进行挽救的比较接口, 需要单独定义一个比较规则类, 定义有 compare() 方法, equals() 方法

实现案例

package com.cwq.beyond;

import java.util.Arrays;
import java.util.Comparator;

class Person{
	private String name;
	private int age;
	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
	public int getAge() {
		return age;
	}
	public String getName() {
		return name;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	
}

class PersonComparator implements Comparator<Person>{

	@Override
	public int compare(Person o1, Person o2) {
		if (o1.getAge() > o2.getAge()) {
			return 1;
		}else if (o1.getAge() < o2.getAge()) {
			return -1;
		}
		return 0;
		
	}
	
}

public class ComparatorDemo {
	public static void main(String[] args) {
		Person data[] = new Person[]{
			new Person("张三", 18),
			new Person("王宏", 55),
			new Person("王五", 19)
		};
		Arrays.sort(data,new PersonComparator());
		System.out.println(Arrays.toString(data));
	}
}