Mastering Apache Commons Lang StringUtils: Hidden Empty/Blank Checks Explained

Overview

The org.apache.commons.lang3.StringUtils class in Apache Commons Lang offers a set of null‑safe methods for checking whether a CharSequence is empty or blank. In addition to the classic isEmpty and isBlank, the library provides multi‑argument variants isAnyEmpty, isNoneEmpty, isAnyBlank and isNoneBlank that evaluate collections of strings in a single call.

isEmpty Series

StringUtils.isEmpty(CharSequence cs) returns true when the argument is null or has a length of zero. A single space character is **not** considered empty.

/**
 * Returns true if the CharSequence is null or empty.
 * Since 3.0 the signature accepts CharSequence.
 */
public static boolean isEmpty(final CharSequence cs) {
    return cs == null || cs.length() == 0;
}

Typical results:

StringUtils.isEmpty(null) = true

StringUtils.isEmpty("") = true

StringUtils.isEmpty(" ") = false

StringUtils.isEmpty("bob") = false

StringUtils.isNotEmpty(CharSequence cs) is the logical negation of isEmpty:

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

StringUtils.isAnyEmpty(CharSequence... css) returns true if **any** supplied element is null or empty.

StringUtils.isAnyEmpty(null) = true

StringUtils.isAnyEmpty(null, "foo") = true

StringUtils.isAnyEmpty("", "bar") = true

StringUtils.isAnyEmpty("bob", "") = true

StringUtils.isAnyEmpty(" ", "bar") = false

StringUtils.isNoneEmpty(CharSequence... css) returns true only when **all** arguments are non‑null and non‑empty; it is implemented as the negation of isAnyEmpty:

/**
 * Checks that none of the CharSequences are empty or null.
 */
public static boolean isNoneEmpty(final CharSequence... css) {
    return !isAnyEmpty(css);
}

isBlank Series

StringUtils.isBlank(CharSequence cs) treats null, the empty string, and strings consisting solely of whitespace as blank.

StringUtils.isBlank(null) = true

StringUtils.isBlank("") = true

StringUtils.isBlank(" ") = true

StringUtils.isBlank("bob") = false

StringUtils.isNotBlank(CharSequence cs) is the negation of isBlank:

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

StringUtils.isAnyBlank(CharSequence... css) returns true if **any** argument is blank (null, empty, or whitespace‑only). The implementation checks for an empty array first, then iterates over the arguments.

/**
 * Returns true if any CharSequence 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(CharSequence... css) returns true only when **all** arguments are non‑blank; it is the logical negation of isAnyBlank:

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

Reference

Full Javadoc for StringUtils is available at: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html