What's the best way to check if a String represents an integer in Java?

Question

I normally use the following idiom to check if a String can be converted to an integer.

public boolean isInteger( String input ) {
    try {
        Integer.         


        

Answer 1

If you are using the Android API you can use:

TextUtils.isDigitsOnly(str);

Answer 2

How about:

return Pattern.matches("-?\\d+", input);

Answer 3

You may try apache utils

NumberUtils.isCreatable(myText)

See the javadoc here

Answer 4

You just check NumberFormatException:-

 String value="123";
 try  
 {  
    int s=Integer.parseInt(any_int_val);
    // do something when integer values comes 
 }  
 catch(NumberFormatException nfe)  
 {  
          // do something when string values comes 
 }  

Answer 5

You probably need to take the use case in account too:

If most of the time you expect numbers to be valid, then catching the exception is only causing a performance overhead when attempting to convert invalid numbers. Whereas calling some isInteger() method and then convert using Integer.parseInt() will always cause a performance overhead for valid numbers - the strings are parsed twice, once by the check and once by the conversion.

Answer 6

This is shorter, but shorter isn't necessarily better (and it won't catch integer values which are out of range, as pointed out in danatel's comment):

input.matches("^-?\\d+$");

Personally, since the implementation is squirrelled away in a helper method and correctness trumps length, I would just go with something like what you have (minus catching the base Exception class rather than NumberFormatException).