Verify if String is hexadecimal

Question

I have a String like \"09a\" and I need a method to confirm if the text is hexadecimal. The code I\'ve posted does something similar, it verifies that a string is a decimal

Answer 1

Here some code for different options and execution time results (JDK 8):

execution time isHex1: 4540
execution time isHex2: 420
execution time isHex3: 7907
execution time regex: 46827

Test code:

@Test
public void testPerformance() {
    int count = 100000000;
    char[] chars = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
    };
    String regexString = new String(chars);
    Pattern pattern = Pattern.compile("^[0-9a-fA-F]+$");
    long start = System.currentTimeMillis();
    for (int i = 0; i < count; i++) {
        for (char c: chars) {
            isHex1(c);
        }
    }
    System.out.println("execution time isHex1: " + (System.currentTimeMillis() - start));
    start = System.currentTimeMillis();
    for (int i = 0; i < count; i++) {
        for (char c: chars) {
            isHex2(c);
        }
    }
    System.out.println("execution time isHex2: " + (System.currentTimeMillis() - start));
    for (int i = 0; i < count; i++) {
        for (char c: chars) {
            isHex3(c);
        }
    }
    System.out.println("execution time isHex3: " + (System.currentTimeMillis() - start));
    for (int i = 0; i < count; i++) {
        Matcher matcher = pattern.matcher(regexString);
        matcher.matches();
    }
    System.out.println("execution time regex: " + (System.currentTimeMillis() - start));
}

private boolean isHex1(char c) {
    return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F');
}

private boolean isHex2(char c) {
    switch (c) {
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
        case 'a':
        case 'b':
        case 'c':
        case 'd':
        case 'e':
        case 'f':
        case 'A':
        case 'B':
        case 'C':
        case 'D':
        case 'E':
        case 'F':
            return true;
        default:
            return false;
    }
}

private boolean isHex3(char c) {
    return (Character.digit(c, 16) != -1);
}