Understanding Apache Commons Lang StringUtils isEmpty/isBlank Methods in Java

StringUtils isEmpty Series

The isEmpty method checks whether a CharSequence is null or has length zero; 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

Implementation:

/**
 * NOTE: This method changed in Lang version 2.0.
 * It no longer trims the CharSequence. That functionality is available in isBlank().
 * @param cs the CharSequence to check, may be null
 * @return true if the CharSequence is empty or null
 */
public static boolean isEmpty(final CharSequence cs) {
    return cs == null || cs.length() == 0;
}

StringUtils.isNotEmpty()

Returns the opposite of isEmpty .

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

/**
 * @param css the CharSequences to check, may be null or empty
 * @return true if any of the CharSequences are empty or null
 */
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 supplied CharSequences are non‑empty and non‑null.

/**
 * Checks if none of the CharSequences are empty ("") or null.
 */
public static boolean isNoneEmpty(final CharSequence... css) {
    // implementation omitted for brevity – it returns !isAnyEmpty(css)
}

StringUtils isBlank Series

StringUtils.isBlank()

Checks whether a CharSequence is null, empty, or consists solely of whitespace characters.

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

/**
 * Checks if a CharSequence is whitespace, empty ("") or null.
 */
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;
}

StringUtils.isNotBlank()

Equivalent to !isBlank(cs) , i.e., the string contains 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

/**
 * Checks if any one of the CharSequences are blank ("") or null and whitespace only.
 */
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 all supplied CharSequences are non‑blank (no null, empty, or whitespace only).

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

Other StringUtils Methods

For a complete list of utilities, refer to the official Apache Commons Lang documentation.

Apache Commons Lang StringUtils Javadoc