一道需要仔细看的java面试题

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public static void main(String[] args) {         Map<String, Object> resultMap = new HashMap<String, Object>();         String str = MapUtil.getStr(resultMap, "yyyy");         System.out.println("++"+str);         System.out.println("++"+str instanceof String);         System.out.println("++"+str == null);         System.out.println("++"+"null".equals(str)); }

　

 

 

 

 

 

 

 

 

 

 

 

结果是：

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++null true false ++false