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

Just one comment about regexp. Every example provided here is wrong!. If you want to use regexp don't forget that compiling the pattern take a lot of time. This:

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

and also this:

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

causes compile of pattern in every method call. To used it correctly follow:

import java.util.regex.Pattern;

/**
 * @author Rastislav Komara
 */
public class NaturalNumberChecker {
    public static final Pattern PATTERN = Pattern.compile("^\\d+$");

    boolean isNaturalNumber(CharSequence input) {
        return input != null && PATTERN.matcher(input).matches();
    }
}