java - 通用compareTo对不同对象类进行排序

Question

我正在尝试使用compareTo返回各种类型对象的最大或最大值。这适用于整数、字符串，但当我尝试包含圆圈时，我遇到了...

如何获得一种通用方法来比较所有对象？在这种情况下，圆只有一个变量，半径，可以进行比较......

public class CompareToVariousObjects {
	public static void main(String[] args) {
		
	Integer[] numbers = {1, -2, 3, 0, -1, 2, -3};
	String[] colors = {"blue", "green", "white", "red", "black"};
	Circle[] circles = {new Circle(5.9), new Circle(.5), new Circle(1), 
			new Circle(2.5), new Circle(.1)};
	
	System.out.println("Numerically, the maximum number is: " + max(numbers));
	System.out.println("Alphabetically, the maximum color is: " + max(colors));
	System.out.println("The largest circle has a radius of: " + max(circles);
	}
	
	public static <T extends Comparable<T>> T max(T[] list) {
		T currentMax = null;
		int currentMaxIndex;
				
		for (int i = 0; i < list.length - 1; i++) {
			currentMax = list[i];
			currentMaxIndex = i;
			
			for (int j = i + 1; j < list.length; j++) {
				if (currentMax.compareTo(list[j]) > 0) {
					currentMax = list[j];
					currentMaxIndex = j;
				}
			}
			
			if (currentMaxIndex != i) {
				list[currentMaxIndex] = list[i];
				list[i] = currentMax;
			}
		}
		return currentMax;
	}
}

Answer 1

“如何获得一种通用方法来比较所有对象？”

没有一种通用的方法来比较对象，这就是为什么首先创建了compareTo和Comparable。考虑一个类的学生，我可以根据高度、分数、年龄来比较他们......

只需创建一个您想要的概念类(例如一个圆圈)，实现 Comparable 并定义compareTo 来定义如何比较该对象的标准。例如:

public class Circle implements Comparable<Circle> {
 int diameter;
 //constructor
 public int compareTo(Circle c) {
   if(c.diameter> this.diameter){
   return 1;
  }else if ....