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

/**
 * 兩個類要想比較大小，
 * 就必須實現Comparable<T>介面，型別引數T通常設為實現該介面的類名
 * 實現Comparable<T>介面後，還要覆蓋public int compareTo(<T> object)方法
 *		如果兩個物件相等返回0
 *		當前物件大於方法傳過來的物件時，返回一個正整數
 *      當前物件小於方法傳過來的物件時，返回一個負整數
 *		而且相等時必須和equals()方法保持一致，即eaquls()方法要返回true
 *		否則相反
 */
public class comparablePoint implements Comparable<comparablePoint>{
	public int x;
	public int y;
	public comparablePoint(int x,int y)
	{
		this.x=x;
		this.y=y;
	}
	public int compareTo(comparablePoint point)
	{
		int s1=x*x+y*y;
		int s2=point.x-point.x+point.y*point.y;
		return s1-s2;
	}
	public String toString()
	{
		return "["+x+","+y+"]";
	}
	public static void main(String args[])
	{
		if(new comparablePoint(3, 4).compareTo(new comparablePoint(1, 1))>0)
			System.out.println("true");
		//線性表
		List<comparablePoint> points=new ArrayList<comparablePoint>();
		points.add(new comparablePoint(1, 6));
		points.add(new comparablePoint(3, 4));
		points.add(new comparablePoint(5, 2));
		System.out.println(points);
		Collections.sort(points);//呼叫Collections工具類進行排序
		System.out.println("排序後的情況");
		System.out.println(points);
	}
}
 

結果

true
[[1,6], [3,4], [5,2]]
排序後的情況
[[3,4], [5,2], [1,6]]