title: How to check if the value is integer in java?
body: <p>I'm using some API by restTemplate. The API returns a key whose type is integer. </p>
  
  <p>But I'm not sure of that value, so I want to check whether the key is really an integer or not.
  I think it might be a string. </p>
  
  <p>What is the best way of checking if the value is really integer?</p>
  
  <p>added:
  I mean that some API might return value like below.
  {id : 10} or {id : "10"}</p>