Exploring Apache Commons Lang StringUtils: isEmpty, isBlank, and Related Methods

The article presents a concise guide to the org.apache.commons.lang3.StringUtils utility class, focusing on its string‑checking methods and providing concrete examples for each.

isEmpty series

StringUtils.isEmpty(null) = true

StringUtils.isEmpty("") = true

StringUtils.isEmpty(" ") = false

Implementation:

public static boolean isEmpty(final CharSequence cs) {
    return cs == null || cs.length() == 0;
}

isNotEmpty

public static boolean isNotEmpty(final CharSequence cs) {
    return !isEmpty(cs);
}

isAnyEmpty returns true if any supplied CharSequence is null or empty.

StringUtils.isAnyEmpty(null) = true
StringUtils.isAnyEmpty(null, "foo") = true
StringUtils.isAnyEmpty("", "bar") = true
StringUtils.isAnyEmpty("bob", "") = true
StringUtils.isAnyEmpty("bob", null) = true
StringUtils.isAnyEmpty(" ", "bar") = false
StringUtils.isAnyEmpty("foo", "bar") = false

Implementation:

public static boolean isAnyEmpty(final CharSequence... css) {
    if (ArrayUtils.isEmpty(css)) {
        return true;
    }
    for (final CharSequence cs : css) {
        if (isEmpty(cs)) {
            return true;
        }
    }
    return false;
}

isNoneEmpty is the logical opposite of isAnyEmpty – it returns true only when all inputs are non‑empty.

public static boolean isNoneEmpty(final CharSequence... css) {
    return !isAnyEmpty(css);
}

isBlank series

StringUtils.isBlank(null) = true

StringUtils.isBlank("") = true

StringUtils.isBlank(" ") = true

Implementation:

public static boolean isBlank(final CharSequence cs) {
    int strLen;
    if (cs == null || (strLen = cs.length()) == 0) {
        return true;
    }
    for (int i = 0; i < strLen; i++) {
        if (!Character.isWhitespace(cs.charAt(i))) {
            return false;
        }
    }
    return true;
}

isNotBlank simply negates isBlank :

public static boolean isNotBlank(final CharSequence cs) {
    return !isBlank(cs);
}

isAnyBlank checks whether any argument is null , empty, or whitespace‑only.

StringUtils.isAnyBlank(null) = true
StringUtils.isAnyBlank(null, "foo") = true
StringUtils.isAnyBlank(null, null) = true
StringUtils.isAnyBlank("", "bar") = true
StringUtils.isAnyBlank("bob", "") = true
StringUtils.isAnyBlank("bob", null) = true
StringUtils.isAnyBlank(" ", "bar") = true
StringUtils.isAnyBlank("foo", "bar") = false

Implementation:

public static boolean isAnyBlank(final CharSequence... css) {
    if (ArrayUtils.isEmpty(css)) {
        return true;
    }
    for (final CharSequence cs : css) {
        if (isBlank(cs)) {
            return true;
        }
    }
    return false;
}

isNoneBlank returns true only when all inputs are non‑blank.

public static boolean isNoneBlank(final CharSequence... css) {
    return !isAnyBlank(css);
}

The article concludes by recommending the official Apache Commons Lang documentation for a complete reference.

Reference: Apache Commons Lang StringUtils Javadoc