hashmaptest.java

java培训专题

package util;
import java.util.*;
/*
 * HashMap继承自Map,而Map与Collection没有任何关系,因此它没有add()方法.
 * 但有put(Object key,Object o)方法以键值对的形式获取数据,通过get(key)来
 * 获取key对应的对象元素. 
 */
public class HashMapTest {
	public static void printElements(Collection c){
		Iterator it=c.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
	}
	public static void main(String[] args) {
		HashMap hm=new HashMap();
		hm.put("one", "zhangsan");
		hm.put("two", "wangwu");
		hm.put("three", "lishi");
        System.out.println(hm.get("one"));
        System.out.println(hm.get("two"));
        System.out.println(hm.get("three"));
        
        Set keys=hm.keySet();
        System.out.println("keys:-------------------------------");
        printElements(keys);//打印出键的视图.
       
        Collection values=hm.values();
        System.out.println("values:------------------------------");
        printElements(values);//打印出值的视图.
        
        Set entry=hm.entrySet();
        System.out.println("entrySet:----------------------------");
        printElements(entry);//打印出键值对的视图.
        Iterator it=entry.iterator();
        System.out.println("-----------");
        while(it.hasNext()){
        	Map.Entry me=(Map.Entry)it.next();
        	System.out.println(me.getKey()+":"+me.getValue());
        }
	}

}