JAVA 8 Map的使用

import java.util.HashMap;import java.util.Iterator;import java.util.Map;public class Test {    public static void main(String[] args) {         Map userMap=new HashMap();         userMap.put("Tom", "boy");         userMap.put("Mary", "girl");         String sex=(String) userMap.get("Tom");         System.out.println(sex);         Iterator iter=userMap.keySet().iterator();         while(iter.hasNext()){             Object key=iter.next();             Object val=userMap.get(key);             System.out.println((String)key);             System.out.println((String)val);         }    }}