Understanding Apache Commons StringUtils: isEmpty, isBlank, and Related Methods

A new colleague with three years of Java experience still confuses the differences between isEmpty and isBlank , using them indiscriminately. The article invites readers to explore the comprehensive utility class org.apache.commons.lang3.StringUtils together.

isEmpty series

StringUtils.isEmpty()

Determines whether a CharSequence is null or has a length of 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

StringUtils.isNotEmpty()

Returns the logical negation of isEmpty() .

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

StringUtils.isAnyEmpty()

Evaluates to true if any of the supplied CharSequence arguments 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 arguments are non‑null and non‑empty, i.e., the opposite of isAnyEmpty() .

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

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

StringUtils.isNotBlank()

Logical negation of isBlank() .

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

StringUtils.isAnyBlank()

Returns true if any argument 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()

Evaluates to true only when none of the arguments are 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:

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