java集合 TreeMap 使用自然排序和定制排序

你的名字 2022-06-12 13:07 278阅读 0赞

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), "王尼玛");
        	treeMap.put(new IdNumber2(1001), "万尼玛");
        	treeMap.put(new IdNumber2(1002), "蓝尼玛");
        	treeMap.put(new IdNumber2(1003), "冯尼玛");
        	treeMap.put(new IdNumber2(1004), "秦尼玛");
        	System.out.println("treeMap="+treeMap);
        	System.out.println("使用定制排序：（从小到大排序）");
        	//使用钉子排序，指明比较器
        	TreeMap<IdNumber2, String> treeMap2=
        			new TreeMap<IdNumber2,String>(new MyComparatorBigToSmall());
        	treeMap2.put(new IdNumber2(1000), "王尼玛");
        	treeMap2.put(new IdNumber2(1001), "万尼玛");
        	treeMap2.put(new IdNumber2(1002), "蓝尼玛");
        	treeMap2.put(new IdNumber2(1003), "冯尼玛");
        	treeMap2.put(new IdNumber2(1004), "秦尼玛");
        	System.out.println("treeMap2="+treeMap2);
        	System.out.println("使用定制排序：（从大到小排序）");
        	TreeMap<IdNumber2, String> treeMap3=
        			new TreeMap<IdNumber2,String>(new MyComparatorSmallToBig());
        	treeMap3.put(new IdNumber2(1000), "王尼玛");
        	treeMap3.put(new IdNumber2(1001), "万尼玛");
        	treeMap3.put(new IdNumber2(1002), "蓝尼玛");
        	treeMap3.put(new IdNumber2(1003), "冯尼玛");
        	treeMap3.put(new IdNumber2(1004), "秦尼玛");
        	System.out.println("treeMap2="+treeMap3);
        }  
    }  
      //自定义比较器:实现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();//从小到大排序
    	}
    } 
    class MyComparatorSmallToBig implements Comparator<IdNumber2>
    {
    	@Override
    	public int compare(IdNumber2 o1, IdNumber2 o2) {
    		// TODO Auto-generated method stub
    		return o2.getIdNumber()-o1.getIdNumber();//从小到大排序
    	}
    }
    //z作为键的类实现Comparable接口
    class IdNumber2 implements Comparable<IdNumber2>
    {
    	//成员属性
    	private int IdNumber;
    	public int getIdNumber()
    	{
    		return IdNumber;
    	}
    	//构造函数
    	public IdNumber2() {
    		// TODO Auto-generated constructor stub
    	}
    	//构造函数
    	public IdNumber2(int IdNumber)
    	{
    		this.IdNumber=IdNumber;
    	}
    	//重写toString()方法
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return "["+this.IdNumber+"]";
    	}
    	//重写equals()方法
    	@Override
    	public boolean equals(Object obj) 
    	{
    		if(obj==this)//自己和自己比较
    			return true;//那就是同一个相等了
    		//传入的引用不为空，而且两个的类型一样
    		if(obj!=null&&obj.getClass()==this.getClass())
    		{
    			IdNumber2 idNumber2=(IdNumber2) obj;//类型转换
    			return this.IdNumber==idNumber2.IdNumber;
    			//如果两个的编号一样，那就认为相等
    		}
    		return false;
    	}
    	//重写hashCode()方法
    	@Override
    	public int hashCode() {
    		// TODO Auto-generated method stub
    		return this.IdNumber*100;
    	}
    	//重写compareTo()方法实现自然排序
    	@Override
    	public int compareTo(IdNumber2 o) 
    	{
    		// TODO Auto-generated method stub
    		//return this.IdNumber-o.IdNumber;//从小到大排序：
    		return o.IdNumber-this.IdNumber;//从大到小排序
    	}
    }