判断一个key 是否在map中存在

public class Test {

	/**
	* @param args
	*/
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		HashMap map = new HashMap();
		map.put("key1", "value1");
		map.put("key2", "value2");
		map.put("key3", "value3");
		Iterator keys = map.keySet().iterator();
		while(keys.hasNext()){
			String key = (String)keys.next();
			if("key2".equals(key)){
				System.out.println("这里面有key2");
			}
		}
	}

}