HashTable四种遍历方式

package coreJava;  

import java.util.Enumeration;  
import java.util.Hashtable;  
import java.util.Iterator;  
/* 
 * 处理原则:先取出key,再利用key获取value 
 */  
public class HashtableDemo {  
    public static void main(String[] args) {  
        Hashtable ht = new Hashtable();  
        for(int i = 0;i<10;i++){  
        ht.put("key"+i, "value"+i);  
        }  
        //利用循环遍历出key和value  
        for(Iterator itr = ht.keySet().iterator();itr.hasNext();){  
            String key = (String)itr.next();  
            String value = (String)ht.get(key);  
            System.out.println(key+" (for) "+value);  
        }  
        //利用循环遍历出key和value  
        Iterator itr = ht.keySet().iterator();  
        while (itr.hasNext()){  
            String str = (String)itr.next();  
            System.out.println(str+" (while) "+ht.get(str));  
        }  
        //利用枚举获取value  
        Enumeration e = ht.elements();  
        while(e.hasMoreElements()){  
            System.out.println(e.nextElement());  
        }  
        //利用枚举获取key:value对儿  
        Enumeration e2 = ht.keys();  
        while(e2.hasMoreElements()){  
            String key = e2.nextElement();  
            System.out.println(key+" = "+ht.get(key));  
        }  
    }  

}