Mastering Apache Commons Lang StringUtils: Empty, Blank, and Their Variants

The org.apache.commons.lang3.StringUtils class provides null‑safe utilities for common string checks and transformations in Java.

isEmpty Series

StringUtils.isEmpty returns true when the supplied CharSequence is null or has a length of zero. Whitespace characters are considered non‑empty.

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

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

StringUtils.isNotEmpty is the logical negation of isEmpty.

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

StringUtils.isAnyEmpty returns true if **any** of the provided CharSequence arguments is null or empty. An empty array is also treated as 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

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;
}

StringUtils.isNoneEmpty returns true only when **all** arguments are non‑empty; it is equivalent to !isAnyEmpty(css).

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

isBlank Series

StringUtils.isBlank treats null, empty strings, and strings consisting solely of whitespace as blank.

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

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

StringUtils.isNotBlank is the logical negation of isBlank.

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

StringUtils.isAnyBlank returns true if **any** argument is blank.

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;
}

StringUtils.isNoneBlank returns true only when none of the arguments are blank; it is equivalent to !isAnyBlank(css).

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

Other Frequently Used Methods

Beyond the empty/blank checks, StringUtils offers utilities for trimming, case conversion, searching, joining, splitting, padding, counting matches, and computing Levenshtein distance, among many others. A non‑exhaustive list includes:

trim/strip – remove leading and trailing whitespace.

equals / compare – null‑safe equality checks.

startsWith / endsWith – prefix and suffix checks.

contains / indexOf / lastIndexOf – null‑safe substring searches.

substring / left / right / mid – safe substring extraction.

join / split – convert between strings and arrays.

replace / overlay – replace occurrences of a substring.

appendIfMissing / prependIfMissing – add a suffix or prefix only if absent.

leftPad / rightPad / center / repeat – pad or repeat strings.

upperCase / lowerCase / swapCase / capitalize / uncapitalize – case transformations.

countMatches – count occurrences of a substring.

isAlpha / isNumeric / isWhitespace / isAsciiPrintable – character class checks.

defaultString – provide a default for null inputs.

rotate – circular shift of characters.

reverse / reverseDelimited – reverse a string or delimited sections.

abbreviate – shorten a string with ellipsis.

difference – report the first differing character between two strings.

levenshteinDistance – compute edit distance between two strings.

https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html