IsNullOrWhiteSpace check for Java

Question

I am needing to write my own IsNullOrWhiteSpace check for Java but am wondering if this is the best method to do so

public static boolean isStringNullOrWhiteSpace(String value) {
    if (isStringNullOrEmpty(value)){
        return true;
    }

    for (Character chars : value.toCharArray()){
        if (!Character.isWhitespace(chars)) return false;
    }

    return true;
}

Answer 1

You'd have to check a profiler, but otherwise just iterating over the string would be best, since you then don't have any allocations going on, i.e.:

public static boolean isStringNullOrWhiteSpace(String value) {
    if (value == null) {
        return true;
    }

    for (int i = 0; i < value.length(); i++) {
        if (!Character.isWhitespace(value.charAt(i))) {
            return false;
        }
    }

    return true;
}

Answer 2

I agree that the String should be left out of the name, as this is quite obvious in StringUtils. How about this short version?

public static boolean isNullOrWhiteSpace(String value) {
    return value == null || value.trim().isEmpty();
}

Answer 3

Having "String" in the method name is doubly redundant: first, because it is in a class called StringUtils, and also because the compiler will handle any overloading based on the parameter type. .NET does likewise and calls it IsNullOrWhitespace.

Answer 4

You could generalize it for the CharSequence interface.

public static boolean isNullOrWhitespace(CharSequence value) {
    if (value == null) {
        return true;
    }

    for (int i=0; i < value.length(); i++) {
        if (!Character.isWhitespace(value.charAt(i))) {
            return false;
        }
    }

    return true;
}

Or if you're using Java 8:

public static boolean isNullOrWhitespace(CharSequence value) {
    return value == null || value.codePoints().allMatch(c -> Character.isWhitespace(c));
}

Answer 5

You should be consistent with your coding style. If you use braces {} for single if statements you should use them each time.

You should replace the check isStringNullOrEmpty(value) with (value==null)

public static boolean isStringNullOrWhiteSpace(String value) {
    if (value == null){
        return true;
    }

    for (Character chars : value.toCharArray()){
        if (!Character.isWhitespace(chars)){
             return false;
        }
    }

    return true;
}  

as value.toCharArray() just returns an empty array if value.length() == 0.

For the naming I go with @200_success. You should call it isNullOrWhiteSpace.

Answer 6

Yes, your way of doing the check is fine!

It should be favored over the code snipped in the accepted answer of Nihathrael. That solution is significantly less performant and would be marked as shortcoming by code quality inspection tools. The invocation of trim() may implicate the creation of a new string object.

See also

• https://stackoverflow.com/questions/5819800/whats-the-better-way-to-check-if-a-string-is-empty-than-using-string-trim-len
• http://pmd.sourceforge.net/pmd-4.2.5/rules/strings.html#InefficientEmptyStringCheck

Answer 7

Have you considered using regular expressions? "Best" is always relative in the context of code, but if I were doing it, I might do something like this:

public static boolean isStringNullOrWhiteSpace(String value) {
    final Pattern pattern = Pattern.compile("^\\w*$");    //pattern for 0 or more whitespace characters
    if (value == null || pattern.matcher(value).find()) {
        return true;
    }
    return false;
}

This basically uses a regular expression for zero or more whitespace characters in a string, and checks your value against it; then returns the result. It's built into java.util.regex. Check it out.

Answer 8

The "empty" part can be also checked by using regex — if the entire string is matched by \s*, then it's empty or whitespace.