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.parseInt( input );         return true;     }     catch( Exception e ) {         return false;     } } 

Is it just me, or does this seem a bit hackish? What’s a better way?

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See my answer (with benchmarks, based on the earlier answer by CodingWithSpike) to see why I’ve reversed my position and accepted Jonas Klemming’s answer to this problem. I think this original code will be used by most people because it’s quicker to implement, and more maintainable, but it’s orders of magnitude slower when non-integer data is provided.

Answer 1

If you are not concerned with potential overflow problems this function will perform about 20-30 times faster than using Integer.parseInt().

public static boolean isInteger(String str) {     if (str == null) {         return false;     }     int length = str.length();     if (length == 0) {         return false;     }     int i = 0;     if (str.charAt(0) == '-') {         if (length == 1) {             return false;         }         i = 1;     }     for (; i < length; i++) {         char c = str.charAt(i);         if (c < '0' || c > '9') {             return false;         }     }     return true; }