Class Ascii


  • @GwtCompatible
    public final class Ascii
    extends Object
    Static methods pertaining to ASCII characters (those in the range of values 0x00 through 0x7F), and to strings containing such characters.

    ASCII utilities also exist in other classes of this package:

    • Charsets.US_ASCII specifies the Charset of ASCII characters.
    • CharMatcher.ascii() matches ASCII characters and provides text processing methods which operate only on the ASCII characters of a string.
    Since:
    7.0
    Author:
    Catherine Berry, Gregory Kick
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static byte ACK
      Acknowledge: A communication control character transmitted by a receiver as an affirmative response to a sender.
      static byte BEL
      Bell ('\a'): A character for use when there is a need to call for human attention.
      static byte BS
      Backspace ('\b'): A format effector which controls the movement of the printing position one printing space backward on the same printing line.
      static byte CAN
      Cancel: A control character used to indicate that the data with which it is sent is in error or is to be disregarded.
      static byte CR
      Carriage Return ('\r'): A format effector which controls the movement of the printing position to the first printing position on the same printing line.
      static byte DC1
      Device Control 1.
      static byte DC2
      Device Control 2.
      static byte DC3
      Device Control 3.
      static byte DC4
      Device Control 4.
      static byte DEL
      Delete: This character is used primarily to "erase" or "obliterate" erroneous or unwanted characters in perforated tape.
      static byte DLE
      Data Link Escape: A communication control character which will change the meaning of a limited number of contiguously following characters.
      static byte EM
      End of Medium: A control character associated with the sent data which may be used to identify the physical end of the medium, or the end of the used, or wanted, portion of information recorded on a medium.
      static byte ENQ
      Enquiry: A communication control character used in data communication systems as a request for a response from a remote station.
      static byte EOT
      End of Transmission: A communication control character used to indicate the conclusion of a transmission, which may have contained one or more texts and any associated headings.
      static byte ESC
      Escape: A control character intended to provide code extension (supplementary characters) in general information interchange.
      static byte ETB
      End of Transmission Block: A communication control character used to indicate the end of a block of data for communication purposes.
      static byte ETX
      End of Text: A communication control character used to terminate a sequence of characters started with STX and transmitted as an entity.
      static byte FF
      Form Feed ('\f'): A format effector which controls the movement of the printing position to the first pre-determined printing line on the next form or page.
      static byte FS
      File Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive.
      static byte GS
      Group Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive.
      static byte HT
      Horizontal Tabulation ('\t'): A format effector which controls the movement of the printing position to the next in a series of predetermined positions along the printing line.
      static byte LF
      Line Feed ('\n'): A format effector which controls the movement of the printing position to the next printing line.
      static char MAX
      The maximum value of an ASCII character.
      static char MIN
      The minimum value of an ASCII character.
      static byte NAK
      Negative Acknowledge: A communication control character transmitted by a receiver as a negative response to the sender.
      static byte NL
      Alternate name for LF.
      static byte NUL
      Null ('\0'): The all-zeros character which may serve to accomplish time fill and media fill.
      static byte RS
      Record Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive.
      static byte SI
      Shift In: A control character indicating that the code combinations which follow shall be interpreted according to the standard code table.
      static byte SO
      Shift Out: A control character indicating that the code combinations which follow shall be interpreted as outside of the character set of the standard code table until a Shift In character is reached.
      static byte SOH
      Start of Heading: A communication control character used at the beginning of a sequence of characters which constitute a machine-sensible address or routing information.
      static byte SP
      Space: A normally non-printing graphic character used to separate words.
      static byte SPACE
      Alternate name for SP.
      static byte STX
      Start of Text: A communication control character which precedes a sequence of characters that is to be treated as an entity and entirely transmitted through to the ultimate destination.
      static byte SUB
      Substitute: A character that may be substituted for a character which is determined to be invalid or in error.
      static byte SYN
      Synchronous Idle: A communication control character used by a synchronous transmission system in the absence of any other character to provide a signal from which synchronism may be achieved or retained.
      static byte US
      Unit Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive.
      static byte VT
      Vertical Tabulation ('\v'): A format effector which controls the movement of the printing position to the next in a series of predetermined printing lines.
      static byte XOFF
      Transmission off.
      static byte XON
      Transmission On: Although originally defined as DC1, this ASCII control character is now better known as the XON code used for software flow control in serial communications.
    • Field Detail

      • NUL

        public static final byte NUL
        Null ('\0'): The all-zeros character which may serve to accomplish time fill and media fill. Normally used as a C string terminator.

        Although RFC 20 names this as "Null", note that it is distinct from the C/C++ "NULL" pointer.

        Since:
        8.0
        See Also:
        Constant Field Values
      • SOH

        public static final byte SOH
        Start of Heading: A communication control character used at the beginning of a sequence of characters which constitute a machine-sensible address or routing information. Such a sequence is referred to as the "heading." An STX character has the effect of terminating a heading.
        Since:
        8.0
        See Also:
        Constant Field Values
      • STX

        public static final byte STX
        Start of Text: A communication control character which precedes a sequence of characters that is to be treated as an entity and entirely transmitted through to the ultimate destination. Such a sequence is referred to as "text." STX may be used to terminate a sequence of characters started by SOH.
        Since:
        8.0
        See Also:
        Constant Field Values
      • ETX

        public static final byte ETX
        End of Text: A communication control character used to terminate a sequence of characters started with STX and transmitted as an entity.
        Since:
        8.0
        See Also:
        Constant Field Values
      • EOT

        public static final byte EOT
        End of Transmission: A communication control character used to indicate the conclusion of a transmission, which may have contained one or more texts and any associated headings.
        Since:
        8.0
        See Also:
        Constant Field Values
      • ENQ

        public static final byte ENQ
        Enquiry: A communication control character used in data communication systems as a request for a response from a remote station. It may be used as a "Who Are You" (WRU) to obtain identification, or may be used to obtain station status, or both.
        Since:
        8.0
        See Also:
        Constant Field Values
      • ACK

        public static final byte ACK
        Acknowledge: A communication control character transmitted by a receiver as an affirmative response to a sender.
        Since:
        8.0
        See Also:
        Constant Field Values
      • BEL

        public static final byte BEL
        Bell ('\a'): A character for use when there is a need to call for human attention. It may control alarm or attention devices.
        Since:
        8.0
        See Also:
        Constant Field Values
      • BS

        public static final byte BS
        Backspace ('\b'): A format effector which controls the movement of the printing position one printing space backward on the same printing line. (Applicable also to display devices.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • HT

        public static final byte HT
        Horizontal Tabulation ('\t'): A format effector which controls the movement of the printing position to the next in a series of predetermined positions along the printing line. (Applicable also to display devices and the skip function on punched cards.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • LF

        public static final byte LF
        Line Feed ('\n'): A format effector which controls the movement of the printing position to the next printing line. (Applicable also to display devices.) Where appropriate, this character may have the meaning "New Line" (NL), a format effector which controls the movement of the printing point to the first printing position on the next printing line. Use of this convention requires agreement between sender and recipient of data.
        Since:
        8.0
        See Also:
        Constant Field Values
      • VT

        public static final byte VT
        Vertical Tabulation ('\v'): A format effector which controls the movement of the printing position to the next in a series of predetermined printing lines. (Applicable also to display devices.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • FF

        public static final byte FF
        Form Feed ('\f'): A format effector which controls the movement of the printing position to the first pre-determined printing line on the next form or page. (Applicable also to display devices.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • CR

        public static final byte CR
        Carriage Return ('\r'): A format effector which controls the movement of the printing position to the first printing position on the same printing line. (Applicable also to display devices.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • SO

        public static final byte SO
        Shift Out: A control character indicating that the code combinations which follow shall be interpreted as outside of the character set of the standard code table until a Shift In character is reached.
        Since:
        8.0
        See Also:
        Constant Field Values
      • SI

        public static final byte SI
        Shift In: A control character indicating that the code combinations which follow shall be interpreted according to the standard code table.
        Since:
        8.0
        See Also:
        Constant Field Values
      • DLE

        public static final byte DLE
        Data Link Escape: A communication control character which will change the meaning of a limited number of contiguously following characters. It is used exclusively to provide supplementary controls in data communication networks.
        Since:
        8.0
        See Also:
        Constant Field Values
      • DC1

        public static final byte DC1
        Device Control 1. Characters for the control of ancillary devices associated with data processing or telecommunication systems, more especially switching devices "on" or "off." (If a single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the preferred assignment.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • XON

        public static final byte XON
        Transmission On: Although originally defined as DC1, this ASCII control character is now better known as the XON code used for software flow control in serial communications. The main use is restarting the transmission after the communication has been stopped by the XOFF control code.
        Since:
        8.0
        See Also:
        Constant Field Values
      • DC2

        public static final byte DC2
        Device Control 2. Characters for the control of ancillary devices associated with data processing or telecommunication systems, more especially switching devices "on" or "off." (If a single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the preferred assignment.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • DC3

        public static final byte DC3
        Device Control 3. Characters for the control of ancillary devices associated with data processing or telecommunication systems, more especially switching devices "on" or "off." (If a single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the preferred assignment.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • DC4

        public static final byte DC4
        Device Control 4. Characters for the control of ancillary devices associated with data processing or telecommunication systems, more especially switching devices "on" or "off." (If a single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the preferred assignment.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • NAK

        public static final byte NAK
        Negative Acknowledge: A communication control character transmitted by a receiver as a negative response to the sender.
        Since:
        8.0
        See Also:
        Constant Field Values
      • SYN

        public static final byte SYN
        Synchronous Idle: A communication control character used by a synchronous transmission system in the absence of any other character to provide a signal from which synchronism may be achieved or retained.
        Since:
        8.0
        See Also:
        Constant Field Values
      • ETB

        public static final byte ETB
        End of Transmission Block: A communication control character used to indicate the end of a block of data for communication purposes. ETB is used for blocking data where the block structure is not necessarily related to the processing format.
        Since:
        8.0
        See Also:
        Constant Field Values
      • CAN

        public static final byte CAN
        Cancel: A control character used to indicate that the data with which it is sent is in error or is to be disregarded.
        Since:
        8.0
        See Also:
        Constant Field Values
      • EM

        public static final byte EM
        End of Medium: A control character associated with the sent data which may be used to identify the physical end of the medium, or the end of the used, or wanted, portion of information recorded on a medium. (The position of this character does not necessarily correspond to the physical end of the medium.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • SUB

        public static final byte SUB
        Substitute: A character that may be substituted for a character which is determined to be invalid or in error.
        Since:
        8.0
        See Also:
        Constant Field Values
      • ESC

        public static final byte ESC
        Escape: A control character intended to provide code extension (supplementary characters) in general information interchange. The Escape character itself is a prefix affecting the interpretation of a limited number of contiguously following characters.
        Since:
        8.0
        See Also:
        Constant Field Values
      • FS

        public static final byte FS
        File Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are not specified.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • GS

        public static final byte GS
        Group Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are not specified.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • RS

        public static final byte RS
        Record Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are not specified.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • US

        public static final byte US
        Unit Separator: These four information separators may be used within data in optional fashion, except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are not specified.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • SP

        public static final byte SP
        Space: A normally non-printing graphic character used to separate words. It is also a format effector which controls the movement of the printing position, one printing position forward. (Applicable also to display devices.)
        Since:
        8.0
        See Also:
        Constant Field Values
      • DEL

        public static final byte DEL
        Delete: This character is used primarily to "erase" or "obliterate" erroneous or unwanted characters in perforated tape.
        Since:
        8.0
        See Also:
        Constant Field Values
      • MIN

        public static final char MIN
        The minimum value of an ASCII character.
        Since:
        9.0 (was type int before 12.0)
        See Also:
        Constant Field Values
      • MAX

        public static final char MAX
        The maximum value of an ASCII character.
        Since:
        9.0 (was type int before 12.0)
        See Also:
        Constant Field Values
    • Method Detail

      • isLowerCase

        public static boolean isLowerCase​(char c)
        Indicates whether c is one of the twenty-six lowercase ASCII alphabetic characters between 'a' and 'z' inclusive. All others (including non-ASCII characters) return false.
      • isUpperCase

        public static boolean isUpperCase​(char c)
        Indicates whether c is one of the twenty-six uppercase ASCII alphabetic characters between 'A' and 'Z' inclusive. All others (including non-ASCII characters) return false.
      • truncate

        public static String truncate​(CharSequence seq,
                                      int maxLength,
                                      String truncationIndicator)
        Truncates the given character sequence to the given maximum length. If the length of the sequence is greater than maxLength, the returned string will be exactly maxLength chars in length and will end with the given truncationIndicator. Otherwise, the sequence will be returned as a string with no changes to the content.

        Examples:

        
         Ascii.truncate("foobar", 7, "..."); // returns "foobar"
         Ascii.truncate("foobar", 5, "..."); // returns "fo..."
         

        Note: This method may work with certain non-ASCII text but is not safe for use with arbitrary Unicode text. It is mostly intended for use with text that is known to be safe for use with it (such as all-ASCII text) and for simple debugging text. When using this method, consider the following:

        • it may split surrogate pairs
        • it may split characters and combining characters
        • it does not consider word boundaries
        • if truncating for display to users, there are other considerations that must be taken into account
        • the appropriate truncation indicator may be locale-dependent
        • it is safe to use non-ASCII characters in the truncation indicator
        Throws:
        IllegalArgumentException - if maxLength is less than the length of truncationIndicator
        Since:
        16.0
      • equalsIgnoreCase

        public static boolean equalsIgnoreCase​(CharSequence s1,
                                               CharSequence s2)
        Indicates whether the contents of the given character sequences s1 and s2 are equal, ignoring the case of any ASCII alphabetic characters between 'a' and 'z' or 'A' and 'Z' inclusive.

        This method is significantly faster than String.equalsIgnoreCase(java.lang.String) and should be used in preference if at least one of the parameters is known to contain only ASCII characters.

        Note however that this method does not always behave identically to expressions such as:

        • string.toUpperCase().equals("UPPER CASE ASCII")
        • string.toLowerCase().equals("lower case ascii")

        due to case-folding of some non-ASCII characters (which does not occur in String.equalsIgnoreCase(java.lang.String)). However in almost all cases that ASCII strings are used, the author probably wanted the behavior provided by this method rather than the subtle and sometimes surprising behavior of toUpperCase() and toLowerCase().

        Since:
        16.0