liquibase-core/src/main/java/liquibase/util/StringUtil.java
public static boolean isWhitespace(CharSequence string) {
        if (string == null) {
            return true;
        }
        return StringUtil.trimToNull(string.toString()) == null;
    }
public static boolean isWhitespace(CharSequence string) {
        if (string == null) {
            return true;
        }
        return StringUtil.trimToNull(string.toString()) == null;
    }
Returns true if the given string only consists of whitespace characters (null-safe)
@param string the string to test
@return true if the string is null or only consists of whitespaces.