java自定义容器排序的两种方法

首先说一下排序的返回值的含义。对于参与比较的两个Object,o1和o2,如果函数的返回值为正值,把o1排在o2后面;返回值为负值,把o1排在o2前面。如果返回值是0,按照容器之前的顺序排列。在compareTo中,this相当于o1,传入的Object相当于o2

第一种方法:对于要排序的类实现Comparable接口

package sort;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
//采用实现Comparable接口的方法实现排序
class S1 implements Comparable{
	int x;
	int y;
	S1(int x, int y){
		this.x = x;
		this.y = y;
	}
	//实现排序方法。先比较x,如果相同比较y
	@Override
	public int compareTo(Object o) {
		S1 obj = (S1) o;
		if(x != obj.x)
		{
			return x - obj.x;
		}
		return y - obj.y;
	}
	//重写toStirng方法,改变println时的显示效果
	public String toString(){
		return "("+x+", "+y+")";
	}
}

public class Sort1 {
	public static void main(String[] args) {
		List s1Set = new ArrayList();
		S1 s1 = new S1(3,5);
		S1 s2 = new S1(2,5);
		S1 s3 = new S1(2,2);
		s1Set.add(s1);
		s1Set.add(s2);
		s1Set.add(s3);
		//对容器进行排序的函数
		Collections.sort(s1Set);
		Iterator it = s1Set.iterator();
		while(it.hasNext())
		{
			System.out.println(it.next());
		}
	}
}

 

第二种方法:覆盖Comparator中的compare方法。

package sort;

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

class S2{
	int x;
	int y;
	S2(int x, int y){
		this.x = x;
		this.y = y;
	}
	//重写toStirng方法,改变println时的显示效果
	public String toString(){
		return "("+x+", "+y+")";
	}
}

public class Sort2 {
	public static void main(String[] args) {
		List s2Set = new ArrayList();
		S2 s1 = new S2(3,5);
		S2 s2 = new S2(4,5);
		S2 s3 = new S2(4,2);
		s2Set.add(s1);
		s2Set.add(s2);
		s2Set.add(s3);
		//对容器进行排序的函数
		Collections.sort(s2Set,c);
		Iterator it = s2Set.iterator();
		while(it.hasNext())
		{
			System.out.println(it.next());
		}	
	}
	static Comparator c = new Comparator(){
		public int compare(Object a0, Object a1) {
			S2 s1 = (S2) a0;
			S2 s2 = (S2) a1;
			if(s1.x != s2.x)
			{
				return s1.x - s2.x;
			}
			else
			{
				return s1.y - s2.y;
			}
		}
	};
	
}


 

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