一、概述

Comparable和Comparator都是用来实现比较的，一般用于集合中元素的比较
基本包装类型，Integer、Long以及String都实现了Comparable接口，该接口的排序逻辑必须写在比较对象中，所以又叫自然排序
我们一般集合排序使用的Collections.sort()，默认使用的就是Comparable

 public static <T extends Comparable<? super T>> void sort(List<T> list) {
     list.sort(null);
 }

当然，我们也可以指定比较器，这里使用的就是Comparator了

 public static <T> void sort(List<T> list, Comparator<? super T> c) {
     list.sort(c);
 }

二、实际使用

1、Comparable

定义了对象Forlan，实现了Comparable接口，重写了compareTo(对象)方法

public class Forlan implements Comparable<Forlan> {

	private String name;

	/**
	 * 身高
	 */
	private int height;

	/**
	 * 体重
	 */
	private int weight;

	public Forlan(String name, int height, int weight) {
		this.name = name;
		this.height = height;
		this.weight = weight;
	}

	@Override
	public String toString() {
		return "Forlan{" +
				"name='" + name + '\'' +
				", height=" + height +
				", weight=" + weight +
				'}';
	}

	/**
	 * 比较身高
	 */
	@Override
	public int compareTo(Forlan forlan) {
		return this.height - forlan.height;
	}
}

验证比较器

List<Forlan> list = new ArrayList<>();
Forlan forlan1 = new Forlan("身高低，体重中", 170, 130);
Forlan forlan2 = new Forlan("身高高，体重低", 180, 120);
Forlan forlan3 = new Forlan("身高中，体重高", 175, 140);
list.add(forlan1);
list.add(forlan2);
list.add(forlan3);
Collections.sort(list);
System.out.println(list);

// 运行结果
[Forlan{name='身高低，体重中', height=170, weight=130}, Forlan{name='身高中，体重高', height=175, weight=140}, Forlan{name='身高高，体重低', height=180, weight=120}]

2、Comparator

定义了对象ForlanW，实现了Comparator接口，重写了compare(T o1, T o2)方法

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

public class ForlanW implements Comparator<ForlanW>{

	private String name;

	/**
	 * 身高
	 */
	private int height;

	/**
	 * 体重
	 */
	private int weight;

	public ForlanW(String name, int height, int weight) {
		this.name = name;
		this.height = height;
		this.weight = weight;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getHeight() {
		return height;
	}

	public void setHeight(int height) {
		this.height = height;
	}

	public int getWeight() {
		return weight;
	}

	public void setWeight(int weight) {
		this.weight = weight;
	}

	@Override
	public String toString() {
		return "ForlanComparator{" +
				"name='" + name + '\'' +
				", height=" + height +
				", weight=" + weight +
				'}';
	}

	@Override
	public int compare(ForlanW o1, ForlanW o2) {
		return o1.height - o2.height;
	}

	public static void main(String[] args) {
		List<ForlanW> list = new ArrayList<>();
		ForlanW forlan1 = new ForlanW("身高低，体重中", 170, 130);
		ForlanW forlan2 = new ForlanW("身高高，体重低", 180, 120);
		ForlanW forlan3 = new ForlanW("身高中，体重高", 175, 140);
		list.add(forlan1