Mastering Apache Commons StringUtils: When to Use isEmpty, isBlank, and More

isEmpty series

StringUtils.isEmpty()

Checks whether a CharSequence is null or has a length of zero. Note that a single space character is not considered empty.

StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false

StringUtils.isNotEmpty()

Returns the opposite of isEmpty; true when the CharSequence is not null and not empty.

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

StringUtils.isAnyEmpty()

Returns true if any of the supplied CharSequences 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

StringUtils.isNoneEmpty()

Returns true only when all supplied CharSequences are neither null nor empty (equivalent to !isAnyEmpty).

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

isBlank series

StringUtils.isBlank()

Checks whether a CharSequence is null, empty, or contains only whitespace characters.

StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false

StringUtils.isNotBlank()

Returns the opposite of isBlank; true when the CharSequence has non‑whitespace characters.

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

StringUtils.isAnyBlank()

Returns true if any of the supplied CharSequences 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

StringUtils.isNoneBlank()

Returns true only when none of the supplied CharSequences are null, empty, or whitespace‑only (equivalent to !isAnyBlank).

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

For a complete reference, see the official Apache Commons Lang documentation.