@CheckReturnValue @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:
StandardCharsets.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. 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.
|
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.
|
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.
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.
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.
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.
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.
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.
public static final byte ACK
Acknowledge: A communication control character transmitted by a receiver as an affirmative response to a sender.
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.
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.)
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.)
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.
public static final byte NL
Alternate name for LF
. (LF
is preferred.)
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.)
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.)
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.)
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.
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.
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.
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.)
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.
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.)
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.)
public static final byte XOFF
Transmission off. See XON
for explanation.
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.)
public static final byte NAK
Negative Acknowledge: A communication control character transmitted by a receiver as a negative response to the sender.
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.
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.
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.
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.)
public static final byte SUB
Substitute: A character that may be substituted for a character which is determined to be invalid or in error.
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.
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.)
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.)
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.)
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.)
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.)
public static final byte SPACE
Alternate name for SP
.
public static final byte DEL
Delete: This character is used primarily to “erase” or “obliterate” erroneous or unwanted characters in perforated tape.
public static final char MIN
The minimum value of an ASCII character.
int
before 12.0)public static final char MAX
The maximum value of an ASCII character.
int
before 12.0)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.
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.
public static char toLowerCase(char c)
If the argument is an uppercase ASCII character returns the lowercase equivalent. Otherwise returns the argument.
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.
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.
public static char toUpperCase(char c)
If the argument is a lowercase ASCII character returns the uppercase equivalent. Otherwise returns the argument.
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
.
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
.
@Beta 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:
IllegalArgumentException
- if maxLength
is less than the length of truncationIndicator
@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()
.