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

isEmpty series

StringUtils.isEmpty()

Determines whether a CharSequence is null or has length zero. Note that a string containing only a space is not considered empty.

<code>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;
}
</code>

StringUtils.isNotEmpty()

Returns the opposite of isEmpty.

<code>public static boolean isNotEmpty(final CharSequence cs) {
    return !isEmpty(cs);
}
</code>

StringUtils.isAnyEmpty()

Returns true if any of the supplied CharSequences is null or empty.

<code>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
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;
}
</code>

StringUtils.isNoneEmpty()

Returns true only when none of the supplied CharSequences are null or empty.

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

isBlank series

StringUtils.isBlank()

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

<code>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) {
    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;
}
</code>

StringUtils.isNotBlank()

Negates isBlank.

<code>public static boolean isNotBlank(final CharSequence cs) {
    return !isBlank(cs);
}
</code>

StringUtils.isAnyBlank()

Returns true if any supplied CharSequence is null, empty, or whitespace only.

<code>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;
}
</code>

StringUtils.isNoneBlank()

Returns true only when none of the supplied CharSequences are blank.

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

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