com.google.common.base

Class Ascii

java.lang.Object

com.google.common.base.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:

Craig Berry, Gregory Kick

Field Summary

Fields

Modifier and Type	Field and 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.

Method Summary

Methods

Modifier and Type	Method and Description
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.
static boolean	isLowerCase(char c) Indicates whether c is one of the twenty-six lowercase ASCII alphabetic characters between 'a' and 'z' inclusive.
static boolean	isUpperCase(char c) Indicates whether c is one of the twenty-six uppercase ASCII alphabetic characters between 'A' and 'Z' inclusive.
static char	toLowerCase(char c) If the argument is an uppercase ASCII character returns the lowercase equivalent.
static String	toLowerCase(CharSequence chars) Returns a copy of the input character sequence in which all uppercase ASCII characters have been converted to lowercase.
static String	toLowerCase(String string) Returns a copy of the input string in which all uppercase ASCII characters have been converted to lowercase.
static char	toUpperCase(char c) If the argument is a lowercase ASCII character returns the uppercase equivalent.
static String	toUpperCase(CharSequence chars) Returns a copy of the input character sequence in which all lowercase ASCII characters have been converted to uppercase.
static String	toUpperCase(String string) Returns a copy of the input string in which all lowercase ASCII characters have been converted to uppercase.
static String	truncate(CharSequence seq, int maxLength, String truncationIndicator) Truncates the given character sequence to the given maximum length.

Methods inherited from class java.lang.Object

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

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

NL

public static final byte NL

Alternate name for LF. (LF is preferred.)

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

XOFF

public static final byte XOFF

Transmission off. See XON for explanation.

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

SPACE

public static final byte SPACE

Alternate name for SP.

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

toLowerCase

public static String toLowerCase(String string)

Returns a copy of the input string in which all uppercase ASCII characters have been converted to lowercase. All other characters are copied without modification.

toLowerCase

public static String toLowerCase(CharSequence chars)

Returns a copy of the input character sequence in which all uppercase ASCII characters have been converted to lowercase. All other characters are copied without modification.

Since:

14.0

toLowerCase

public static char toLowerCase(char c)

If the argument is an uppercase ASCII character returns the lowercase equivalent. Otherwise returns the argument.

toUpperCase

public static String toUpperCase(String string)

Returns a copy of the input string in which all lowercase ASCII characters have been converted to uppercase. All other characters are copied without modification.

toUpperCase

public static String toUpperCase(CharSequence chars)

Returns a copy of the input character sequence in which all lowercase ASCII characters have been converted to uppercase. All other characters are copied without modification.

Since:

14.0

toUpperCase

public static char toUpperCase(char c)

If the argument is a lowercase ASCII character returns the uppercase equivalent. Otherwise returns the argument.

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

@Beta
@CheckReturnValue
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

@Beta
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