Java中Comparable与Comparator的区别

悠悠 2022-05-13 17:26 238阅读 0赞

/*
     *java中Comparable & Comparator都是用来实现集合中元素的比较，用来进行排序
     *区别：Comparable是集合中内部定义的方法实现的排序，
     *	   Comparator是外部定义的排序方法，
     *想要实现排序，就要在集合外定义Comparator接口的方法或在集合内实现Comparable接口的方法
     *Comparator位于java.util下
     *Comparable位于java.lang下
     * 
     */
    //方法一：
    @SuppressWarnings("all")
    public class TestCompareTo {
    	public static void main(String[] args) {
    		Circle[] cir = new Circle[4];
    		for (int i = 0; i < cir.length; ++i) {
    			cir[i] = new Circle(Math.random() * 9 + 1);
    		}
    		
    		Arrays.sort(cir,new Comparator() {
    			@Override
    			public int compare(Object o1, Object o2) {
    				Circle c1 = (Circle) o1;
    				Circle c2 = (Circle) o2;
    				if(c1.getRadius()> c2.getRadius()){
    					return 1;
    				}else if(c1.getRadius()< c2.getRadius()){
    					return -1;
    				}
    				return 0;
    			}});
    		for (Circle circle : cir) {
    			System.out.println(circle);
    		}
    	}
    }
    
    class Circle {
    	private double radius;
    
    	public Circle() {
    		super();
    	}
    
    	public Circle(double radius) {
    		super();
    		this.radius = radius;
    	}
    
    	public double getRadius() {
    		return radius;
    	}
    
    	public void setRadius(double radius) {
    		this.radius = radius;
    	}
    
    	@Override
    	public String toString() {
    		return "Circle [radius=" + radius + "]";
    	}
    
    }

//方法二：
    @SuppressWarnings("all")
    public class TestCompareTo2{
    	public static void main(String[] args) {
    		Rectangle[] rec = new Rectangle[3];
    		for(int i=0; i<rec.length; ++i){
    			rec[i] = new Rectangle(10-i, 8-i);
    			
    		}
    		Arrays.sort(rec);
    		for (Rectangle rectangle : rec) {
    			System.out.println(rectangle);
    		}
    	}
    
    }
    
    class Rectangle implements Comparable{
    	private int height;
    	private int width;
    	public Rectangle(int height, int width) {
    		super();
    		this.height = height;
    		this.width = width;
    	}
    	private int getArea(){
    		return height* width;
    	}
    	@Override
    	public String toString() {
    		return "Rectangle [height=" + height + ", width=" + width + "]";
    	}
    
    	@Override
    	public int compareTo(Object o) {
    		Rectangle other = (Rectangle) o;
    		if(this.getArea()> other.getArea()){
    			return 1;
    		}else if(this.getArea() < other.getArea()){
    			return -1;
    		}
    		return 0;
    	}
    	
    	
    }