java中Map迭代的三种方式

//java中Map迭代的三种方式
import java.util.HashMap;
import java.util.Map;

public class Mapdemo{
	public static void main(String[] args){
		Map<String,Integer> map = new HashMap<String,Integer>();
		map.put("first", 1);
		map.put("second", 2);
		map.put("third", 3);
		
		for(Object o:map.values()){       //直接拿到value对象
			int value = (Integer)o;
			System.out.println(value);     
		}
		
		for(Object o:map.keySet()){       //直接拿到key值
			String key = o.toString();
			int value = (Integer) map.get(o);   //通过key，拿到value
			System.out.println(key+"_"+value);
		}
		
		for(Map.Entry<String, Integer> entry:map.entrySet()){
			String key = entry.getKey();
			int value = entry.getValue();
			System.out.println(key+":"+value);
		}
	}
}