Java TreeMap 使用自然排序和定製排序

import java.util.Comparator;
import java.util.TreeMap;
 
public class Demo3 {  
    public static void main(String[] args) 
    {  
    	System.out.println("使用自然排序：");
    	TreeMap<IdNumber2, String> treeMap=new TreeMap<IdNumber2,String>();
    	treeMap.put(new IdNumber2(1000), "王尼瑪");
    	treeMap.put(new IdNumber2(1001), "萬尼瑪");
    	treeMap.put(new IdNumber2(1002), "藍尼瑪");
    	treeMap.put(new IdNumber2(1003), "馮尼瑪");
    	treeMap.put(new IdNumber2(1004), "秦尼瑪");
    	System.out.println("treeMap="+treeMap);
    	System.out.println("使用定製排序：（從小到大排序）");
    	//使用釘子排序，指明比較器
    	TreeMap<IdNumber2, String> treeMap2=
    			new TreeMap<IdNumber2,String>(new MyComparatorBigToSmall());
    	treeMap2.put(new IdNumber2(1000), "王尼瑪");
    	treeMap2.put(new IdNumber2(1001), "萬尼瑪");
    	treeMap2.put(new IdNumber2(1002), "藍尼瑪");
    	treeMap2.put(new IdNumber2(1003), "馮尼瑪");
    	treeMap2.put(new IdNumber2(1004), "秦尼瑪");
    	System.out.println("treeMap2="+treeMap2);
    	System.out.println("使用定製排序：（從大到小排序）");
    	TreeMap<IdNumber2, String> treeMap3=
    			new TreeMap<IdNumber2,String>(new MyComparatorSmallToBig());
    	treeMap3.put(new IdNumber2(1000), "王尼瑪");
    	treeMap3.put(new IdNumber2(1001), "萬尼瑪");
    	treeMap3.put(new IdNumber2(1002), "藍尼瑪");
    	treeMap3.put(new IdNumber2(1003), "馮尼瑪");
    	treeMap3.put(new IdNumber2(1004), "秦尼瑪");
    	System.out.println("treeMap2="+treeMap3);
    }  
}  
  //自定義比較器:實現comparator接口
class MyComparatorBigToSmall implements Comparator<IdNumber2> //使用泛型
{  
 
	@Override
	public int compare(IdNumber2 o1, IdNumber2 o2) {
		// TODO Auto-generated method stub
		return o1.getIdNumber()-o2.getIdNumber();//從小到大排序
	}
} 
class MyComparatorSmallToBig implements Comparator<IdNumber2>
{
	@Override
	public int compare(IdNumber2 o1, IdNumber2 o2) {
		// TODO Auto-generated method stub
		return o2.getIdNumber()-o1.getIdNumber();//從小到大排序
	}
}
//z作爲鍵的類實現Comparable接口
class IdNumber2 implements Comparable<IdNumber2>
{
	//成員屬性
	private int IdNumber;
	public int getIdNumber()
	{
		return IdNumber;
	}
	//構造函數
	public IdNumber2() {
		// TODO Auto-generated constructor stub
	}
	//構造函數
	public IdNumber2(int IdNumber)
	{
		this.IdNumber=IdNumber;
	}
	//重寫toString()方法
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "["+this.IdNumber+"]";
	}
	//重寫equals()方法
	@Override
	public boolean equals(Object obj) 
	{
		if(obj==this)//自己和自己比較
			return true;//那就是同一個相等了
		//傳入的引用不爲空，而且兩個的類型一樣
		if(obj!=null&&obj.getClass()==this.getClass())
		{
			IdNumber2 idNumber2=(IdNumber2) obj;//類型轉換
			return this.IdNumber==idNumber2.IdNumber;
			//如果兩個的編號一樣，那就認爲相等
		}
		return false;
	}
	//重寫hashCode()方法
	@Override
	public int hashCode() {
		// TODO Auto-generated method stub
		return this.IdNumber*100;
	}
	//重寫compareTo()方法實現自然排序
	@Override
	public int compareTo(IdNumber2 o) 
	{
		// TODO Auto-generated method stub
		//return this.IdNumber-o.IdNumber;//從小到大排序：
		return o.IdNumber-this.IdNumber;//從大到小排序
	}
}