HashMap 和TreeMap的比较

HashMap 和TreeMap的比较
与Java相关信息
HashMap的代码为：

import java.util.*; 
public class hashmap { 
    Map calendar = new HashMap(); 
    public hashmap(String d[],String i[]){ 
        for(int j=0;j<d.length;j++){ 
            calendar.put(d[j], i[j]); 
        } 
    } 
    public static void main(String[] args) { 
        String [] dates = {"10/4","05/7","12/7","01/5"}; 
        String [] items = {"Z","Y","X","C"}; 
        hashmap example = new hashmap(dates,items); 
        Set mapping = example.calendar.entrySet(); 
        System.out.println("map= "+example.calendar); 
        System.out.println("Object\tkey\tvalue"); 
        for(Iterator it = mapping.iterator();it.hasNext();){ 
            Map.Entry me = (Map.Entry)it.next(); 
            Object ok = me.getKey(); 
            Object ov = me.getValue(); 
            System.out.print(me+"\t"); 
            System.out.print(ok+"\t"); 
            System.out.println(ov); 
        } 
    } 

} 

HashTree的代码：

import java.util.*; 
public class hashmap { 
    Map calendar = new TreeMap(); 
    public hashmap(String d[],String i[]){ 
        for(int j=0;j<d.length;j++){ 
            calendar.put(d[j], i[j]); 
        } 
    } 
    public static void main(String[] args) { 
        String [] dates = {"10/4","05/7","12/7","01/5"}; 
        String [] items = {"Z","Y","X","C"}; 
        hashmap example = new hashmap(dates,items); 
        Set mapping = example.calendar.entrySet(); 
        System.out.println("map= "+example.calendar); 
        System.out.println("Object\tkey\tvalue"); 
        for(Iterator it = mapping.iterator();it.hasNext();){ 
            Map.Entry me = (Map.Entry)it.next(); 
            Object ok = me.getKey(); 
            Object ov = me.getValue(); 
            System.out.print(me+"\t"); 
            System.out.print(ok+"\t"); 
            System.out.println(ov); 
        } 
    } 

}

代码大致相同，但是HashMap的输出是无序的，TreeMap的输出是按关键字升序排列的！


但是TreeMap的开销也比较HashMap大，因为它要处理排序！