学步园

public class Duck implements Comparable {
	//实现了comparable接口的对象可以使用Arrays.sort(object[])或者Collections.sort(list)进行排序;
	
	private String name;
	private int weight;

	@Override
	public int compareTo(Object o) { // a.comparableTo(b) 与0比较
		Duck oDuck = (Duck) o;
		if(this.weight > oDuck.weight){
			return 1;
		}else if(this.weight < oDuck.weight){
			return -1;
		}else {
			return 0;
		}
	}

	public Duck(String name, int weight) {
		super();
		this.name = name;
		this.weight = weight;
	}

	@Override
	public String toString() {
		return name + "\tweight :  " + weight;
	}
}

测试：

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;

public class MainTest {
	public static void main(String[] args) {
		int numDuck = 3;
		Duck duck[] = new Duck[3];
		duck[0] = new Duck("duck1", 25);
		duck[1] = new Duck("duck2", 23);
		duck[2] = new Duck("duck3", 24);

//		Arrays.sort(duck);   //排序1

               ArrayList<Duck> list = new ArrayList<Duck>();   //排序2
		for (int i = 0; i < 3; i++) {
			list.add(duck[i]);
		}
		Collections.sort(list);
		
		for (int i = 0; i < 3; i++) {
			System.out.println(list.get(i));
		}
	}
}

总结：接口comparable中使用了模板方法模式，在子类中我们只需要实现comparableTo() 方法定义排序的语法规则即可，至于具体的排序算法都由 
模板方法（sort()）来实现。         ====模板方法模式