Package com.google.common.base

Class Strings

  • @GwtCompatible
public final class Strings
extends java.lang.Object
    Static utility methods pertaining to String or CharSequence instances.
    Since:
    3.0
    Author:
    Kevin Bourrillion

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static java.lang.String commonPrefix​(java.lang.CharSequence a, java.lang.CharSequence b)
      Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs.
      static java.lang.String commonSuffix​(java.lang.CharSequence a, java.lang.CharSequence b)
      Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs.
      static java.lang.String emptyToNull​(java.lang.String string)
      Returns the given string if it is nonempty; null otherwise.
      static boolean isNullOrEmpty​(java.lang.String string)
      Returns true if the given string is null or is the empty string.
      static java.lang.String lenientFormat​(java.lang.String template, @Nullable java.lang.Object... args)
      Returns the given template string with each occurrence of "%s" replaced with the corresponding argument value from args; or, if the placeholder and argument counts do not match, returns a best-effort form of that string.
      static java.lang.String nullToEmpty​(java.lang.String string)
      Returns the given string if it is non-null; the empty string otherwise.
      static java.lang.String padEnd​(java.lang.String string, int minLength, char padChar)
      Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length.
      static java.lang.String padStart​(java.lang.String string, int minLength, char padChar)
      Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length.
      static java.lang.String repeat​(java.lang.String string, int count)
      Returns a string consisting of a specific number of concatenated copies of an input string.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • nullToEmpty

        public static java.lang.String nullToEmpty​(@CheckForNull
                                           java.lang.String string)
        Returns the given string if it is non-null; the empty string otherwise.
        Parameters:
        string - the string to test and possibly return
        Returns:
        string itself if it is non-null; "" if it is null

      • emptyToNull

        @CheckForNull
public static java.lang.String emptyToNull​(@CheckForNull
                                           java.lang.String string)
        Returns the given string if it is nonempty; null otherwise.
        Parameters:
        string - the string to test and possibly return
        Returns:
        string itself if it is nonempty; null if it is empty or null

      • isNullOrEmpty

        public static boolean isNullOrEmpty​(@CheckForNull
                                    java.lang.String string)
        Returns true if the given string is null or is the empty string.

        Consider normalizing your string references with nullToEmpty(java.lang.String). If you do, you can use String.isEmpty() instead of this method, and you won't need special null-safe forms of methods like String.toUpperCase(java.util.Locale) either. Or, if you'd like to normalize "in the other direction," converting empty strings to null, you can use emptyToNull(java.lang.String).

        Parameters:
        string - a string reference to check
        Returns:
        true if the string is null or is the empty string

      • padStart

        public static java.lang.String padStart​(java.lang.String string,
                                        int minLength,
                                        char padChar)
        Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length. For example,
        • padStart("7", 3, '0') returns "007"
        • padStart("2010", 3, '0') returns "2010"

        See Formatter for a richer set of formatting capabilities.

        Parameters:
        string - the string which should appear at the end of the result
        minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.
        padChar - the character to insert at the beginning of the result until the minimum length is reached
        Returns:
        the padded string

      • padEnd

        public static java.lang.String padEnd​(java.lang.String string,
                                      int minLength,
                                      char padChar)
        Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length. For example,
        • padEnd("4.", 5, '0') returns "4.000"
        • padEnd("2010", 3, '!') returns "2010"

        See Formatter for a richer set of formatting capabilities.

        Parameters:
        string - the string which should appear at the beginning of the result
        minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.
        padChar - the character to append to the end of the result until the minimum length is reached
        Returns:
        the padded string

      • repeat

        public static java.lang.String repeat​(java.lang.String string,
                                      int count)
        Returns a string consisting of a specific number of concatenated copies of an input string. For example, repeat("hey", 3) returns the string "heyheyhey".
        Parameters:
        string - any non-null string
        count - the number of times to repeat it; a nonnegative integer
        Returns:
        a string containing string repeated count times (the empty string if count is zero)
        Throws:
        java.lang.IllegalArgumentException - if count is negative

      • commonPrefix

        public static java.lang.String commonPrefix​(java.lang.CharSequence a,
                                            java.lang.CharSequence b)
        Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs. If a and b have no common prefix, returns the empty string.
        Since:
        11.0

      • commonSuffix

        public static java.lang.String commonSuffix​(java.lang.CharSequence a,
                                            java.lang.CharSequence b)
        Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs. If a and b have no common suffix, returns the empty string.
        Since:
        11.0

      • lenientFormat

        public static java.lang.String lenientFormat​(@CheckForNull
                                             java.lang.String template,
                                             @CheckForNull
                                             @Nullable java.lang.Object... args)
        Returns the given template string with each occurrence of "%s" replaced with the corresponding argument value from args; or, if the placeholder and argument counts do not match, returns a best-effort form of that string. Will not throw an exception under normal conditions.

        Note: For most string-formatting needs, use String.format, PrintWriter.format, and related methods. These support the full range of format specifiers, and alert you to usage errors by throwing IllegalFormatException.

        In certain cases, such as outputting debugging information or constructing a message to be used for another unchecked exception, an exception during string formatting would serve little purpose except to supplant the real information you were trying to provide. These are the cases this method is made for; it instead generates a best-effort string with all supplied argument values present. This method is also useful in environments such as GWT where String.format is not available. As an example, method implementations of the Preconditions class use this formatter, for both of the reasons just discussed.

        Warning: Only the exact two-character placeholder sequence "%s" is recognized.

        Parameters:
        template - a string containing zero or more "%s" placeholder sequences. null is treated as the four-character string "null".
        args - the arguments to be substituted into the message template. The first argument specified is substituted for the first occurrence of "%s" in the template, and so forth. A null argument is converted to the four-character string "null"; non-null values are converted to strings using Object.toString().
        Since:
        25.1