org.springframework.util

Class StringUtils


  • public abstract class StringUtils
    extends Object
    Miscellaneous String utility methods.

    Mainly for internal use within the framework; consider Jakarta's Commons Lang for a more comprehensive suite of String utilities.

    This class delivers some simple functionality that should really be provided by the core Java String and StringBuilder classes, such as the ability to replace(java.lang.String, java.lang.String, java.lang.String) all occurrences of a given substring in a target string. It also provides easy-to-use methods to convert between delimited strings, such as CSV strings, and collections and arrays.

    Since:
    16 April 2001
    Author:
    Rod Johnson, Juergen Hoeller, Keith Donald, Rob Harrop, Rick Evans, Arjen Poutsma
    • Constructor Detail

      • StringUtils

        public StringUtils()
    • Method Detail

      • isEmpty

        public static boolean isEmpty(Object str)
        Check whether the given String is empty.

        This method accepts any Object as an argument, comparing it to null and the empty String. As a consequence, this method will never return true for a non-null non-String object.

        The Object signature is useful for general attribute handling code that commonly deals with Strings but generally has to iterate over Objects since attributes may e.g. be primitive value objects as well.

        Parameters:
        str - the candidate String
        Since:
        3.2.1
      • hasLength

        public static boolean hasLength(CharSequence str)
        Check that the given CharSequence is neither null nor of length 0. Note: Will return true for a CharSequence that purely consists of whitespace.

         StringUtils.hasLength(null) = false
         StringUtils.hasLength("") = false
         StringUtils.hasLength(" ") = true
         StringUtils.hasLength("Hello") = true
         
        Parameters:
        str - the CharSequence to check (may be null)
        Returns:
        true if the CharSequence is not null and has length
        See Also:
        hasText(String)
      • hasLength

        public static boolean hasLength(String str)
        Check that the given String is neither null nor of length 0. Note: Will return true for a String that purely consists of whitespace.
        Parameters:
        str - the String to check (may be null)
        Returns:
        true if the String is not null and has length
        See Also:
        hasLength(CharSequence)
      • hasText

        public static boolean hasText(CharSequence str)
        Check whether the given CharSequence has actual text. More specifically, returns true if the string not null, its length is greater than 0, and it contains at least one non-whitespace character.

         StringUtils.hasText(null) = false
         StringUtils.hasText("") = false
         StringUtils.hasText(" ") = false
         StringUtils.hasText("12345") = true
         StringUtils.hasText(" 12345 ") = true
         
        Parameters:
        str - the CharSequence to check (may be null)
        Returns:
        true if the CharSequence is not null, its length is greater than 0, and it does not contain whitespace only
        See Also:
        Character.isWhitespace(char)
      • hasText

        public static boolean hasText(String str)
        Check whether the given String has actual text. More specifically, returns true if the string not null, its length is greater than 0, and it contains at least one non-whitespace character.
        Parameters:
        str - the String to check (may be null)
        Returns:
        true if the String is not null, its length is greater than 0, and it does not contain whitespace only
        See Also:
        hasText(CharSequence)
      • containsWhitespace

        public static boolean containsWhitespace(CharSequence str)
        Check whether the given CharSequence contains any whitespace characters.
        Parameters:
        str - the CharSequence to check (may be null)
        Returns:
        true if the CharSequence is not empty and contains at least 1 whitespace character
        See Also:
        Character.isWhitespace(char)
      • containsWhitespace

        public static boolean containsWhitespace(String str)
        Check whether the given String contains any whitespace characters.
        Parameters:
        str - the String to check (may be null)
        Returns:
        true if the String is not empty and contains at least 1 whitespace character
        See Also:
        containsWhitespace(CharSequence)
      • trimWhitespace

        public static String trimWhitespace(String str)
        Trim leading and trailing whitespace from the given String.
        Parameters:
        str - the String to check
        Returns:
        the trimmed String
        See Also:
        Character.isWhitespace(char)
      • trimAllWhitespace

        public static String trimAllWhitespace(String str)
        Trim all whitespace from the given String: leading, trailing, and in between characters.
        Parameters:
        str - the String to check
        Returns:
        the trimmed String
        See Also:
        Character.isWhitespace(char)
      • trimLeadingWhitespace

        public static String trimLeadingWhitespace(String str)
        Trim leading whitespace from the given String.
        Parameters:
        str - the String to check
        Returns:
        the trimmed String
        See Also:
        Character.isWhitespace(char)
      • trimTrailingWhitespace

        public static String trimTrailingWhitespace(String str)
        Trim trailing whitespace from the given String.
        Parameters:
        str - the String to check
        Returns:
        the trimmed String
        See Also:
        Character.isWhitespace(char)
      • trimLeadingCharacter

        public static String trimLeadingCharacter(String str,
                                  char leadingCharacter)
        Trim all occurrences of the supplied leading character from the given String.
        Parameters:
        str - the String to check
        leadingCharacter - the leading character to be trimmed
        Returns:
        the trimmed String
      • trimTrailingCharacter

        public static String trimTrailingCharacter(String str,
                                   char trailingCharacter)
        Trim all occurrences of the supplied trailing character from the given String.
        Parameters:
        str - the String to check
        trailingCharacter - the trailing character to be trimmed
        Returns:
        the trimmed String
      • startsWithIgnoreCase

        public static boolean startsWithIgnoreCase(String str,
                                   String prefix)
        Test if the given String starts with the specified prefix, ignoring upper/lower case.
        Parameters:
        str - the String to check
        prefix - the prefix to look for
        See Also:
        String.startsWith(java.lang.String, int)
      • endsWithIgnoreCase

        public static boolean endsWithIgnoreCase(String str,
                                 String suffix)
        Test if the given String ends with the specified suffix, ignoring upper/lower case.
        Parameters:
        str - the String to check
        suffix - the suffix to look for
        See Also:
        String.endsWith(java.lang.String)
      • substringMatch

        public static boolean substringMatch(CharSequence str,
                             int index,
                             CharSequence substring)
        Test whether the given string matches the given substring at the given index.
        Parameters:
        str - the original string (or StringBuilder)
        index - the index in the original string to start matching against
        substring - the substring to match at the given index
      • countOccurrencesOf

        public static int countOccurrencesOf(String str,
                             String sub)
        Count the occurrences of the substring in string s.
        Parameters:
        str - string to search in. Return 0 if this is null.
        sub - string to search for. Return 0 if this is null.
      • replace

        public static String replace(String inString,
                     String oldPattern,
                     String newPattern)
        Replace all occurrences of a substring within a string with another string.
        Parameters:
        inString - String to examine
        oldPattern - String to replace
        newPattern - String to insert
        Returns:
        a String with the replacements
      • delete

        public static String delete(String inString,
                    String pattern)
        Delete all occurrences of the given substring.
        Parameters:
        inString - the original String
        pattern - the pattern to delete all occurrences of
        Returns:
        the resulting String
      • deleteAny

        public static String deleteAny(String inString,
                       String charsToDelete)
        Delete any character in a given String.
        Parameters:
        inString - the original String
        charsToDelete - a set of characters to delete. E.g. "az\n" will delete 'a's, 'z's and new lines.
        Returns:
        the resulting String
      • quote

        public static String quote(String str)
        Quote the given String with single quotes.
        Parameters:
        str - the input String (e.g. "myString")
        Returns:
        the quoted String (e.g. "'myString'"), or null if the input was null
      • quoteIfString

        public static Object quoteIfString(Object obj)
        Turn the given Object into a String with single quotes if it is a String; keeping the Object as-is else.
        Parameters:
        obj - the input Object (e.g. "myString")
        Returns:
        the quoted String (e.g. "'myString'"), or the input object as-is if not a String
      • unqualify

        public static String unqualify(String qualifiedName)
        Unqualify a string qualified by a '.' dot character. For example, "this.name.is.qualified", returns "qualified".
        Parameters:
        qualifiedName - the qualified name
      • unqualify

        public static String unqualify(String qualifiedName,
                       char separator)
        Unqualify a string qualified by a separator character. For example, "this:name:is:qualified" returns "qualified" if using a ':' separator.
        Parameters:
        qualifiedName - the qualified name
        separator - the separator
      • capitalize

        public static String capitalize(String str)
        Capitalize a String, changing the first letter to upper case as per Character.toUpperCase(char). No other letters are changed.
        Parameters:
        str - the String to capitalize, may be null
        Returns:
        the capitalized String, null if null
      • uncapitalize

        public static String uncapitalize(String str)
        Uncapitalize a String, changing the first letter to lower case as per Character.toLowerCase(char). No other letters are changed.
        Parameters:
        str - the String to uncapitalize, may be null
        Returns:
        the uncapitalized String, null if null
      • getFilename

        public static String getFilename(String path)
        Extract the filename from the given path, e.g. "mypath/myfile.txt" -> "myfile.txt".
        Parameters:
        path - the file path (may be null)
        Returns:
        the extracted filename, or null if none
      • getFilenameExtension

        public static String getFilenameExtension(String path)
        Extract the filename extension from the given path, e.g. "mypath/myfile.txt" -> "txt".
        Parameters:
        path - the file path (may be null)
        Returns:
        the extracted filename extension, or null if none
      • stripFilenameExtension

        public static String stripFilenameExtension(String path)
        Strip the filename extension from the given path, e.g. "mypath/myfile.txt" -> "mypath/myfile".
        Parameters:
        path - the file path (may be null)
        Returns:
        the path with stripped filename extension, or null if none
      • applyRelativePath

        public static String applyRelativePath(String path,
                               String relativePath)
        Apply the given relative path to the given path, assuming standard Java folder separation (i.e. "/" separators).
        Parameters:
        path - the path to start from (usually a full file path)
        relativePath - the relative path to apply (relative to the full file path above)
        Returns:
        the full file path that results from applying the relative path
      • cleanPath

        public static String cleanPath(String path)
        Normalize the path by suppressing sequences like "path/.." and inner simple dots.

        The result is convenient for path comparison. For other uses, notice that Windows separators ("\") are replaced by simple slashes.

        Parameters:
        path - the original path
        Returns:
        the normalized path
      • pathEquals

        public static boolean pathEquals(String path1,
                         String path2)
        Compare two paths after normalization of them.
        Parameters:
        path1 - first path for comparison
        path2 - second path for comparison
        Returns:
        whether the two paths are equivalent after normalization
      • parseLocaleString

        public static Locale parseLocaleString(String localeString)
        Parse the given localeString value into a Locale.

        This is the inverse operation of Locale's toString.

        Parameters:
        localeString - the locale String, following Locale's toString() format ("en", "en_UK", etc); also accepts spaces as separators, as an alternative to underscores
        Returns:
        a corresponding Locale instance
        Throws:
        IllegalArgumentException - in case of an invalid locale specification
      • toLanguageTag

        public static String toLanguageTag(Locale locale)
        Determine the RFC 3066 compliant language tag, as used for the HTTP "Accept-Language" header.
        Parameters:
        locale - the Locale to transform to a language tag
        Returns:
        the RFC 3066 compliant language tag as String
      • addStringToArray

        public static String[] addStringToArray(String[] array,
                                String str)
        Append the given String to the given String array, returning a new array consisting of the input array contents plus the given String.
        Parameters:
        array - the array to append to (can be null)
        str - the String to append
        Returns:
        the new array (never null)
      • concatenateStringArrays

        public static String[] concatenateStringArrays(String[] array1,
                                       String[] array2)
        Concatenate the given String arrays into one, with overlapping array elements included twice.

        The order of elements in the original arrays is preserved.

        Parameters:
        array1 - the first array (can be null)
        array2 - the second array (can be null)
        Returns:
        the new array ( null if both given arrays were null)
      • mergeStringArrays

        public static String[] mergeStringArrays(String[] array1,
                                 String[] array2)
        Merge the given String arrays into one, with overlapping array elements only included once.

        The order of elements in the original arrays is preserved (with the exception of overlapping elements, which are only included on their first occurrence).

        Parameters:
        array1 - the first array (can be null)
        array2 - the second array (can be null)
        Returns:
        the new array ( null if both given arrays were null)
      • sortStringArray

        public static String[] sortStringArray(String[] array)
        Turn given source String array into sorted array.
        Parameters:
        array - the source array
        Returns:
        the sorted array (never null)
      • toStringArray

        public static String[] toStringArray(Collection<String> collection)
        Copy the given Collection into a String array. The Collection must contain String elements only.
        Parameters:
        collection - the Collection to copy
        Returns:
        the String array ( null if the passed-in Collection was null)
      • toStringArray

        public static String[] toStringArray(Enumeration<String> enumeration)
        Copy the given Enumeration into a String array. The Enumeration must contain String elements only.
        Parameters:
        enumeration - the Enumeration to copy
        Returns:
        the String array ( null if the passed-in Enumeration was null)
      • trimArrayElements

        public static String[] trimArrayElements(String[] array)
        Trim the elements of the given String array, calling String.trim() on each of them.
        Parameters:
        array - the original String array
        Returns:
        the resulting array (of the same size) with trimmed elements
      • removeDuplicateStrings

        public static String[] removeDuplicateStrings(String[] array)
        Remove duplicate Strings from the given array. Also sorts the array, as it uses a TreeSet.
        Parameters:
        array - the String array
        Returns:
        an array without duplicates, in natural sort order
      • split

        public static String[] split(String toSplit,
                     String delimiter)
        Split a String at the first occurrence of the delimiter. Does not include the delimiter in the result.
        Parameters:
        toSplit - the string to split
        delimiter - to split the string up with
        Returns:
        a two element array with index 0 being before the delimiter, and index 1 being after the delimiter (neither element includes the delimiter); or null if the delimiter wasn't found in the given input String
      • splitArrayElementsIntoProperties

        public static Properties splitArrayElementsIntoProperties(String[] array,
                                                  String delimiter)
        Take an array Strings and split each element based on the given delimiter. A Properties instance is then generated, with the left of the delimiter providing the key, and the right of the delimiter providing the value.

        Will trim both the key and value before adding them to the Properties instance.

        Parameters:
        array - the array to process
        delimiter - to split each element using (typically the equals symbol)
        Returns:
        a Properties instance representing the array contents, or null if the array to process was null or empty
      • splitArrayElementsIntoProperties

        public static Properties splitArrayElementsIntoProperties(String[] array,
                                                  String delimiter,
                                                  String charsToDelete)
        Take an array Strings and split each element based on the given delimiter. A Properties instance is then generated, with the left of the delimiter providing the key, and the right of the delimiter providing the value.

        Will trim both the key and value before adding them to the Properties instance.

        Parameters:
        array - the array to process
        delimiter - to split each element using (typically the equals symbol)
        charsToDelete - one or more characters to remove from each element prior to attempting the split operation (typically the quotation mark symbol), or null if no removal should occur
        Returns:
        a Properties instance representing the array contents, or null if the array to process was null or empty
      • tokenizeToStringArray

        public static String[] tokenizeToStringArray(String str,
                                     String delimiters)
        Tokenize the given String into a String array via a StringTokenizer. Trims tokens and omits empty tokens.

        The given delimiters string is supposed to consist of any number of delimiter characters. Each of those characters can be used to separate tokens. A delimiter is always a single character; for multi-character delimiters, consider using delimitedListToStringArray

        Parameters:
        str - the String to tokenize
        delimiters - the delimiter characters, assembled as String (each of those characters is individually considered as delimiter).
        Returns:
        an array of the tokens
        See Also:
        StringTokenizer, String.trim(), delimitedListToStringArray(java.lang.String, java.lang.String)
      • tokenizeToStringArray

        public static String[] tokenizeToStringArray(String str,
                                     String delimiters,
                                     boolean trimTokens,
                                     boolean ignoreEmptyTokens)
        Tokenize the given String into a String array via a StringTokenizer.

        The given delimiters string is supposed to consist of any number of delimiter characters. Each of those characters can be used to separate tokens. A delimiter is always a single character; for multi-character delimiters, consider using delimitedListToStringArray

        Parameters:
        str - the String to tokenize
        delimiters - the delimiter characters, assembled as String (each of those characters is individually considered as delimiter)
        trimTokens - trim the tokens via String's trim
        ignoreEmptyTokens - omit empty tokens from the result array (only applies to tokens that are empty after trimming; StringTokenizer will not consider subsequent delimiters as token in the first place).
        Returns:
        an array of the tokens ( null if the input String was null)
        See Also:
        StringTokenizer, String.trim(), delimitedListToStringArray(java.lang.String, java.lang.String)
      • delimitedListToStringArray

        public static String[] delimitedListToStringArray(String str,
                                          String delimiter)
        Take a String which is a delimited list and convert it to a String array.

        A single delimiter can consists of more than one character: It will still be considered as single delimiter string, rather than as bunch of potential delimiter characters - in contrast to tokenizeToStringArray.

        Parameters:
        str - the input String
        delimiter - the delimiter between elements (this is a single delimiter, rather than a bunch individual delimiter characters)
        Returns:
        an array of the tokens in the list
        See Also:
        tokenizeToStringArray(java.lang.String, java.lang.String)
      • delimitedListToStringArray

        public static String[] delimitedListToStringArray(String str,
                                          String delimiter,
                                          String charsToDelete)
        Take a String which is a delimited list and convert it to a String array.

        A single delimiter can consists of more than one character: It will still be considered as single delimiter string, rather than as bunch of potential delimiter characters - in contrast to tokenizeToStringArray.

        Parameters:
        str - the input String
        delimiter - the delimiter between elements (this is a single delimiter, rather than a bunch individual delimiter characters)
        charsToDelete - a set of characters to delete. Useful for deleting unwanted line breaks: e.g. "\r\n\f" will delete all new lines and line feeds in a String.
        Returns:
        an array of the tokens in the list
        See Also:
        tokenizeToStringArray(java.lang.String, java.lang.String)
      • commaDelimitedListToStringArray

        public static String[] commaDelimitedListToStringArray(String str)
        Convert a CSV list into an array of Strings.
        Parameters:
        str - the input String
        Returns:
        an array of Strings, or the empty array in case of empty input
      • commaDelimitedListToSet

        public static Set<String> commaDelimitedListToSet(String str)
        Convenience method to convert a CSV string list to a set. Note that this will suppress duplicates.
        Parameters:
        str - the input String
        Returns:
        a Set of String entries in the list
      • collectionToDelimitedString

        public static String collectionToDelimitedString(Collection<?> coll,
                                         String delim,
                                         String prefix,
                                         String suffix)
        Convenience method to return a Collection as a delimited (e.g. CSV) String. E.g. useful for toString() implementations.
        Parameters:
        coll - the Collection to display
        delim - the delimiter to use (probably a ",")
        prefix - the String to start each element with
        suffix - the String to end each element with
        Returns:
        the delimited String
      • collectionToDelimitedString

        public static String collectionToDelimitedString(Collection<?> coll,
                                         String delim)
        Convenience method to return a Collection as a delimited (e.g. CSV) String. E.g. useful for toString() implementations.
        Parameters:
        coll - the Collection to display
        delim - the delimiter to use (probably a ",")
        Returns:
        the delimited String
      • collectionToCommaDelimitedString

        public static String collectionToCommaDelimitedString(Collection<?> coll)
        Convenience method to return a Collection as a CSV String. E.g. useful for toString() implementations.
        Parameters:
        coll - the Collection to display
        Returns:
        the delimited String
      • arrayToDelimitedString

        public static String arrayToDelimitedString(Object[] arr,
                                    String delim)
        Convenience method to return a String array as a delimited (e.g. CSV) String. E.g. useful for toString() implementations.
        Parameters:
        arr - the array to display
        delim - the delimiter to use (probably a ",")
        Returns:
        the delimited String
      • arrayToCommaDelimitedString

        public static String arrayToCommaDelimitedString(Object[] arr)
        Convenience method to return a String array as a CSV String. E.g. useful for toString() implementations.
        Parameters:
        arr - the array to display
        Returns:
        the delimited String