String to Integer without needing exception handling

StringToIntegerValidator.java

/*
 * Copyright (C) 2014 Matthew Roberts
 * MIT License, http://opensource.org/licenses/MIT
 */

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Checks to see if a String can be used as a valid Integer without resorting to
 * exception handling.
 * 
 * @author mroberts
 */
public class StringToIntegerValidator {
 
    private static final String INTEGER_PATTERN = "(-)?(\\d){1,19}$";
 
    public boolean isInteger(String stringNumber) {
 
        boolean isInteger = false;
 
        Pattern pattern = Pattern.compile(INTEGER_PATTERN,
                Pattern.CASE_INSENSITIVE);
        Matcher matcher = pattern.matcher(stringNumber);
 
        if (matcher.matches()) {
 
            long longNumber = Long.parseLong(stringNumber);
 
            if (longNumber <= Integer.MAX_VALUE && longNumber >= Integer.MIN_VALUE) {
                isInteger = true;
            }
        }
 
        return isInteger;
    }
}

StringToIntegerValidatorTest.java

/*
 * Copyright (C) 2014 Matthew Roberts
 * MIT License, http://opensource.org/licenses/MIT
 */
public class StringToIntegerValidatorTest extends TestCase {
 
    @Test
    public void validIntegerTest() {
 
        StringToIntegerValidator validator = new StringToIntegerValidator();
        Boolean isValidInteger = null;
 
        isValidInteger = validator.isInteger("2147483647");
        assertTrue(isValidInteger.equals(true));
 
        isValidInteger = validator.isInteger("-42");
        assertTrue(isValidInteger.equals(true));
 
        isValidInteger = validator.isInteger("0");
        assertTrue(isValidInteger.equals(true));
    }
 
    @Test
    public void invalidIntegerTest() {
 
        StringToIntegerValidator validator = new StringToIntegerValidator();
        Boolean isValidInteger = null;
 
        isValidInteger = validator.isInteger("Not an int.");
        assertTrue(isValidInteger.equals(false));
 
        isValidInteger = validator.isInteger("123045678.5");
        assertTrue(isValidInteger.equals(false));
 
        isValidInteger = validator.isInteger("123456789123456789");
        assertTrue(isValidInteger.equals(false));
    }
}