How to check if the value is integer in java? [dup

问题:

This question already has answers here:

Determine if object is integer (3 answers)

Closed 2 years ago.

I'm using some API by restTemplate. The API returns a key whose type is integer.

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.

What is the best way of checking if the value is really integer?

added: I mean that some API might return value like below. {id : 10} or {id : "10"}

回答1:

Object x = someApi();

if (x instanceof Integer) 

Note that if someApi() returns type Integer the only possibilities of something returned are:

• an Integer
• null

In which case you can:

if (x == null) {
    // not an Integer
} else {
    // yes an Integer
}

回答2:

If what you receive is a String, you can try to parse it into an integer, if it fails, it's because it was not an integer after all. Something like this:

public static boolean isInteger(String str) {
    try {
        Integer.parseInt(str);
        return true;
    } catch (NumberFormatException nfe) {
        return false;
    }
}

回答3:

One possibility is to use Integer.valueOf(String)

回答4:

Assuming your API return value can either be an Integer or String you can do something like this:

Integer getValue(Object valueFromAPI){
    return (valueFromAPI != null ? Integer.valueOf(valueFromAPI.toString()) : null); 
}