Determine if a String is an Integer in Java [duplicate]

Answer 1

You can use Integer.parseInt(str) and catch the NumberFormatException if the string is not a valid integer, in the following fashion (as pointed out by all answers):

static boolean isInt(String s)
{
 try
  { int i = Integer.parseInt(s); return true; }

 catch(NumberFormatException er)
  { return false; }
}

However, note here that if the evaluated integer overflows, the same exception will be thrown. Your purpose was to find out whether or not, it was a valid integer. So its safer to make your own method to check for validity:

static boolean isInt(String s)  // assuming integer is in decimal number system
{
 for(int a=0;a