How to cast to Number from String in java without knowing which number type is present in the String?

<p>

I am writing a compiler, that reads from an input file, parses it and creates various kind of tokens. Further, in parsing, upon getting a NumLitToken , I retrieve its's number value stored as String and want to save it as a Number for further stages of transformations. <br> <br>
I am not aware whether the String contains int/ float / long / double etc. so i am using NumberFormat.getInstance().parse(x) method and expecting appropriate casted value, but i don't know why i am not getting a cast to Integer for int values.<br>
Also, if there is any other way better to cast to Number from String, please enlighten me about it.

</p>

A small extract:

import java.text.*;
public class Main
{
	public static void main(String[] args) throws ParseException{
		String x = "100";
		Number o  = NumberFormat.getInstance().parse(x);
		System.out.println(o.getClass().toString());
		if(o instanceof Integer){
		    System.out.println("int");
		}
	}
}

Output:

class java.lang.Long

<hr>
<p>

UPDATE : Turns out, the method only returns long or double. What to do to get appropriate cast to Number ? Is there a better way rather than trying to cast for every number type?

</p>

Because the docs say so:

> Returns a Long is possible, otherwise a Double

Simple as that.

If you're just trying to parse an int, int x = Integer.parseInt("500"); does the job!

As mentioned in a different answer it is how it works.

If you want to a function that returns the most appropriate type depending its size the apache-commons NumberUtils.createNumber will do that for you.