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Class HexFormat

java.lang.Object
java.util.HexFormat
public final class HexFormat extends Object
HexFormat converts between bytes and chars and hex-encoded strings which may include additional formatting markup such as prefixes, suffixes, and delimiters.

There are two factories of HexFormat with preset parameters of() and ofDelimiter(delimiter). For other parameter combinations the withXXX methods return copies of HexFormat modified withPrefix(String), withSuffix(String), withDelimiter(String) or choice of withUpperCase() or withLowerCase() parameters.

For primitive to hexadecimal string conversions the toHexDigits methods include toHexDigits(byte), toHexDigits(int), and toHexDigits(long), etc. The default is to use lowercase characters "0-9","a-f". For conversions producing uppercase hexadecimal the characters are "0-9","A-F". Only the HexFormat.isUpperCase() parameter is considered; the delimiter, prefix and suffix are not used.

For hexadecimal string to primitive conversions the fromHexDigits methods include fromHexDigits(string), fromHexDigitsToLong(string), and fromHexDigit(int) converts a single character or codepoint. For conversions from hexadecimal characters the digits and uppercase and lowercase characters in "0-9", "a-f", and "A-F" are converted to corresponding values 0-15. The delimiter, prefix, suffix, and uppercase parameters are not used.

For byte array to formatted hexadecimal string conversions the formatHex methods include formatHex(byte[]) and formatHex(Appendable, byte[]). The formatted output is a string or is appended to an Appendable such as StringBuilder or PrintStream. Each byte value is formatted as the prefix, two hexadecimal characters from the uppercase or lowercase digits, and the suffix. A delimiter follows each formatted value, except the last. For conversions producing uppercase hexadecimal strings use withUpperCase().

For formatted hexadecimal string to byte array conversions the parseHex methods include parseHex(CharSequence) and parseHex(char[], offset, length). Each byte value is parsed from the prefix, two case insensitive hexadecimal characters, and the suffix. A delimiter follows each formatted value, except the last.

API Note:
For example, an individual byte is converted to a string of hexadecimal digits using toHexDigits(int) and converted from a string to a primitive value using fromHexDigits(string).

     HexFormat hex = HexFormat.of();
     byte b = 127;
     String byteStr = hex.toHexDigits(b);

     byte byteVal = (byte)hex.fromHexDigits(byteStr);
     assert(byteStr.equals("7f"));
     assert(b == byteVal);

     // The hexadecimal digits are: "7f"
 

For a comma (", ") separated format with a prefix ("#") using lowercase hex digits the HexFormat is:


     HexFormat commaFormat = HexFormat.ofDelimiter(", ").withPrefix("#");
     byte[] bytes = {0, 1, 2, 3, 124, 125, 126, 127};
     String str = commaFormat.formatHex(bytes);

     byte[] parsed = commaFormat.parseHex(str);
     assert(Arrays.equals(bytes, parsed));

     // The formatted string is: "#00, #01, #02, #03, #7c, #7d, #7e, #7f"
 

For a fingerprint of byte values that uses the delimiter colon (":") and uppercase characters the HexFormat is:


     HexFormat formatFingerprint = HexFormat.ofDelimiter(":").withUpperCase();
     byte[] bytes = {0, 1, 2, 3, 124, 125, 126, 127};
     String str = formatFingerprint.formatHex(bytes);
     byte[] parsed = formatFingerprint.parseHex(str);
     assert(Arrays.equals(bytes, parsed));

     // The formatted string is: "00:01:02:03:7C:7D:7E:7F"
 

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of HexFormat may have unpredictable results and should be avoided. The equals method should be used for comparisons.

This class is immutable and thread-safe.

Unless otherwise noted, passing a null argument to any method will cause a NullPointerException to be thrown.

Since:
17

Method Summary

Modifier and Type Method Description
String delimiter()
Returns the delimiter between hexadecimal values in formatted hexadecimal strings.
boolean equals(Object o)
Returns true if the other object is a HexFormat with the same parameters.
String formatHex(byte[] bytes)
Returns a hexadecimal string formatted from a byte array.
String formatHex(byte[] bytes, int fromIndex, int toIndex)
Returns a hexadecimal string formatted from a byte array range.
<A extends Appendable>
A
formatHex(A out, byte[] bytes)
Appends formatted hexadecimal strings from a byte array to the Appendable.
<A extends Appendable>
A
formatHex(A out, byte[] bytes, int fromIndex, int toIndex)
Appends formatted hexadecimal strings from a byte array range to the Appendable.
static int fromHexDigit(int ch)
Returns the value for the hexadecimal character or codepoint.
static int fromHexDigits(CharSequence string)
Returns the int value parsed from a string of up to eight hexadecimal characters.
static int fromHexDigits(CharSequence string, int fromIndex, int toIndex)
Returns the int value parsed from a string range of up to eight hexadecimal characters.
static long fromHexDigitsToLong(CharSequence string)
Returns the long value parsed from a string of up to sixteen hexadecimal characters.
static long fromHexDigitsToLong(CharSequence string, int fromIndex, int toIndex)
Returns the long value parsed from a string range of up to sixteen hexadecimal characters.
int hashCode()
Returns a hashcode for this HexFormat.
static boolean isHexDigit(int ch)
Returns true if the character is a valid hexadecimal character or codepoint.
boolean isUpperCase()
Returns true if the hexadecimal digits are uppercase, otherwise false.
static HexFormat of()
Returns a hexadecimal formatter with no delimiter and lowercase characters.
static HexFormat ofDelimiter(String delimiter)
Returns a hexadecimal formatter with the delimiter and lowercase characters.
byte[] parseHex(char[] chars, int fromIndex, int toIndex)
Returns a byte array containing hexadecimal values parsed from a range of the character array.
byte[] parseHex(CharSequence string)
Returns a byte array containing hexadecimal values parsed from the string.
byte[] parseHex(CharSequence string, int fromIndex, int toIndex)
Returns a byte array containing hexadecimal values parsed from a range of the string.
String prefix()
Returns the prefix used for each hexadecimal value in formatted hexadecimal strings.
String suffix()
Returns the suffix used for each hexadecimal value in formatted hexadecimal strings.
String toHexDigits(byte value)
Returns the two hexadecimal characters for the byte value.
String toHexDigits(char value)
Returns the four hexadecimal characters for the char value.
String toHexDigits(int value)
Returns the eight hexadecimal characters for the int value.
String toHexDigits(long value)
Returns the sixteen hexadecimal characters for the long value.
String toHexDigits(long value, int digits)
Returns up to sixteen hexadecimal characters for the long value.
String toHexDigits(short value)
Returns the four hexadecimal characters for the short value.
<A extends Appendable>
A
toHexDigits(A out, byte value)
Appends two hexadecimal characters for the byte value to the Appendable.
char toHighHexDigit(int value)
Returns the hexadecimal character for the high 4 bits of the value considering it to be a byte.
char toLowHexDigit(int value)
Returns the hexadecimal character for the low 4 bits of the value considering it to be a byte.
String toString()
Returns a description of the formatter parameters for uppercase, delimiter, prefix, and suffix.
HexFormat withDelimiter(String delimiter)
Returns a copy of this HexFormat with the delimiter.
HexFormat withLowerCase()
Returns a copy of this HexFormat to use lowercase hexadecimal characters.
HexFormat withPrefix(String prefix)
Returns a copy of this HexFormat with the prefix.
HexFormat withSuffix(String suffix)
Returns a copy of this HexFormat with the suffix.
HexFormat withUpperCase()
Returns a copy of this HexFormat to use uppercase hexadecimal characters.

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Details

of

public static HexFormat of()
Returns a hexadecimal formatter with no delimiter and lowercase characters. The delimiter, prefix, and suffix are empty. The methods withDelimiter, withUpperCase, withLowerCase, withPrefix, and withSuffix return copies of formatters with new parameters.
Returns:
a hexadecimal formatter with no delimiter and lowercase characters

ofDelimiter

public static HexFormat ofDelimiter(String delimiter)
Returns a hexadecimal formatter with the delimiter and lowercase characters. The prefix and suffix are empty. The methods withDelimiter, withUpperCase, withLowerCase, withPrefix, and withSuffix return copies of formatters with new parameters.
Parameters:
delimiter - a delimiter, non-null, may be empty
Returns:
a HexFormat with the delimiter and lowercase characters

withDelimiter

public HexFormat withDelimiter(String delimiter)
Returns a copy of this HexFormat with the delimiter.
Parameters:
delimiter - the delimiter, non-null, may be empty
Returns:
a copy of this HexFormat with the delimiter

withPrefix

public HexFormat withPrefix(String prefix)
Returns a copy of this HexFormat with the prefix.
Parameters:
prefix - a prefix, non-null, may be empty
Returns:
a copy of this HexFormat with the prefix

withSuffix

public HexFormat withSuffix(String suffix)
Returns a copy of this HexFormat with the suffix.
Parameters:
suffix - a suffix, non-null, may be empty
Returns:
a copy of this HexFormat with the suffix

withUpperCase

public HexFormat withUpperCase()
Returns a copy of this HexFormat to use uppercase hexadecimal characters. The uppercase hexadecimal characters are "0-9", "A-F".
Returns:
a copy of this HexFormat with uppercase hexadecimal characters

withLowerCase

public HexFormat withLowerCase()
Returns a copy of this HexFormat to use lowercase hexadecimal characters. The lowercase hexadecimal characters are "0-9", "a-f".
Returns:
a copy of this HexFormat with lowercase hexadecimal characters

delimiter

public String delimiter()
Returns the delimiter between hexadecimal values in formatted hexadecimal strings.
Returns:
the delimiter, non-null, may be empty ""

prefix

public String prefix()
Returns the prefix used for each hexadecimal value in formatted hexadecimal strings.
Returns:
the prefix, non-null, may be empty ""

suffix

public String suffix()
Returns the suffix used for each hexadecimal value in formatted hexadecimal strings.
Returns:
the suffix, non-null, may be empty ""

isUpperCase

public boolean isUpperCase()
Returns true if the hexadecimal digits are uppercase, otherwise false.
Returns:
true if the hexadecimal digits are uppercase, otherwise false

formatHex

public String formatHex(byte[] bytes)
Returns a hexadecimal string formatted from a byte array. Each byte value is formatted as the prefix, two hexadecimal characters selected from uppercase or lowercase digits, and the suffix. A delimiter follows each formatted value, except the last. The behavior is equivalent to formatHex(bytes, 0, bytes.length)).
Parameters:
bytes - a non-null array of bytes
Returns:
a string hexadecimal formatting of the byte array

formatHex

public String formatHex(byte[] bytes, int fromIndex, int toIndex)
Returns a hexadecimal string formatted from a byte array range. Each byte value is formatted as the prefix, two hexadecimal characters selected from uppercase or lowercase digits, and the suffix. A delimiter follows each formatted value, except the last.
Parameters:
bytes - a non-null array of bytes
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive
Returns:
a string hexadecimal formatting each byte of the array range
Throws:
IndexOutOfBoundsException - if the array range is out of bounds

formatHex

public <A extends Appendable> A formatHex(A out, byte[] bytes)
Appends formatted hexadecimal strings from a byte array to the Appendable. Each byte value is formatted as the prefix, two hexadecimal characters selected from uppercase or lowercase digits, and the suffix. A delimiter follows each formatted value, except the last. The formatted hexadecimal strings are appended in zero or more calls to the Appendable methods.
Type Parameters:
A - The type of Appendable
Parameters:
out - an Appendable, non-null
bytes - a byte array
Returns:
the Appendable
Throws:
UncheckedIOException - if an I/O exception occurs appending to the output

formatHex

public <A extends Appendable> A formatHex(A out, byte[] bytes, int fromIndex, int toIndex)
Appends formatted hexadecimal strings from a byte array range to the Appendable. Each byte value is formatted as the prefix, two hexadecimal characters selected from uppercase or lowercase digits, and the suffix. A delimiter follows each formatted value, except the last. The formatted hexadecimal strings are appended in zero or more calls to the Appendable methods.
Type Parameters:
A - The type of Appendable
Parameters:
out - an Appendable, non-null
bytes - a byte array, non-null
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive.
Returns:
the Appendable
Throws:
IndexOutOfBoundsException - if the array range is out of bounds
UncheckedIOException - if an I/O exception occurs appending to the output

parseHex

public byte[] parseHex(CharSequence string)
Returns a byte array containing hexadecimal values parsed from the string. Each byte value is parsed from the prefix, two case insensitive hexadecimal characters, and the suffix. A delimiter follows each formatted value, except the last. The delimiters, prefixes, and suffixes strings must be present; they may be empty strings. A valid string consists only of the above format.
Parameters:
string - a string containing the byte values with prefix, hexadecimal digits, suffix, and delimiters
Returns:
a byte array with the values parsed from the string
Throws:
IllegalArgumentException - if the prefix or suffix is not present for each byte value, the byte values are not hexadecimal characters, or if the delimiter is not present after all but the last byte value

parseHex

public byte[] parseHex(CharSequence string, int fromIndex, int toIndex)
Returns a byte array containing hexadecimal values parsed from a range of the string. Each byte value is parsed from the prefix, two case insensitive hexadecimal characters, and the suffix. A delimiter follows each formatted value, except the last. The delimiters, prefixes, and suffixes strings must be present; they may be empty strings. A valid string consists only of the above format.
Parameters:
string - a string range containing hexadecimal digits, delimiters, prefix, and suffix.
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive.
Returns:
a byte array with the values parsed from the string range
Throws:
IllegalArgumentException - if the prefix or suffix is not present for each byte value, the byte values are not hexadecimal characters, or if the delimiter is not present after all but the last byte value
IndexOutOfBoundsException - if the string range is out of bounds

parseHex

public byte[] parseHex(char[] chars, int fromIndex, int toIndex)
Returns a byte array containing hexadecimal values parsed from a range of the character array. Each byte value is parsed from the prefix, two case insensitive hexadecimal characters, and the suffix. A delimiter follows each formatted value, except the last. The delimiters, prefixes, and suffixes strings must be present; they may be empty strings. A valid character array range consists only of the above format.
Parameters:
chars - a character array range containing an even number of hexadecimal digits, delimiters, prefix, and suffix.
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive.
Returns:
a byte array with the values parsed from the character array range
Throws:
IllegalArgumentException - if the prefix or suffix is not present for each byte value, the byte values are not hexadecimal characters, or if the delimiter is not present after all but the last byte value
IndexOutOfBoundsException - if the character array range is out of bounds

toLowHexDigit

public char toLowHexDigit(int value)
Returns the hexadecimal character for the low 4 bits of the value considering it to be a byte. If the parameter isUpperCase() is true the character returned for values 10-15 is uppercase "A-F", otherwise the character returned is lowercase "a-f". The values in the range 0-9 are returned as "0-9".
Parameters:
value - a value, only the low 4 bits 0-3 of the value are used
Returns:
the hexadecimal character for the low 4 bits 0-3 of the value

toHighHexDigit

public char toHighHexDigit(int value)
Returns the hexadecimal character for the high 4 bits of the value considering it to be a byte. If the parameter isUpperCase() is true the character returned for values 10-15 is uppercase "A-F", otherwise the character returned is lowercase "a-f". The values in the range 0-9 are returned as "0-9".
Parameters:
value - a value, only bits 4-7 of the value are used
Returns:
the hexadecimal character for the bits 4-7 of the value

toHexDigits

public <A extends Appendable> A toHexDigits(A out, byte value)
Appends two hexadecimal characters for the byte value to the Appendable. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The hexadecimal characters are appended in one or more calls to the Appendable methods. The delimiter, prefix and suffix are not used.
Type Parameters:
A - The type of Appendable
Parameters:
out - an Appendable, non-null
value - a byte value
Returns:
the Appendable
Throws:
UncheckedIOException - if an I/O exception occurs appending to the output

toHexDigits

public String toHexDigits(byte value)
Returns the two hexadecimal characters for the byte value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - a byte value
Returns:
the two hexadecimal characters for the byte value

toHexDigits

public String toHexDigits(char value)
Returns the four hexadecimal characters for the char value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - a char value
Returns:
the four hexadecimal characters for the char value

toHexDigits

public String toHexDigits(short value)
Returns the four hexadecimal characters for the short value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - a short value
Returns:
the four hexadecimal characters for the short value

toHexDigits

public String toHexDigits(int value)
Returns the eight hexadecimal characters for the int value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - an int value
Returns:
the eight hexadecimal characters for the int value
See Also:

toHexDigits

public String toHexDigits(long value)
Returns the sixteen hexadecimal characters for the long value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - a long value
Returns:
the sixteen hexadecimal characters for the long value
See Also:

toHexDigits

public String toHexDigits(long value, int digits)
Returns up to sixteen hexadecimal characters for the long value. Each nibble (4 bits) from most significant to least significant of the value is formatted as if by toLowHexDigit(nibble). The delimiter, prefix and suffix are not used.
Parameters:
value - a long value
digits - the number of hexadecimal digits to return, 0 to 16
Returns:
the hexadecimal characters for the long value
Throws:
IllegalArgumentException - if digits is negative or greater than 16

isHexDigit

public static boolean isHexDigit(int ch)
Returns true if the character is a valid hexadecimal character or codepoint. The valid hexadecimal characters are:
  • '0' ('\u0030') through '9' ('\u0039') inclusive,
  • 'A' ('\u0041') through 'F' ('\u0046') inclusive, and
  • 'a' ('\u0061') through 'f' ('\u0066') inclusive.
Parameters:
ch - a codepoint
Returns:
true if the character is valid a hexadecimal character, otherwise false

fromHexDigit

public static int fromHexDigit(int ch)
Returns the value for the hexadecimal character or codepoint. The value is:
  • (ch - '0') for '0' through '9' inclusive,
  • (ch - 'A' + 10) for 'A' through 'F' inclusive, and
  • (ch - 'a' + 10) for 'a' through 'f' inclusive.
Parameters:
ch - a character or codepoint
Returns:
the value 0-15
Throws:
NumberFormatException - if the codepoint is not a hexadecimal character

fromHexDigits

public static int fromHexDigits(CharSequence string)
Returns the int value parsed from a string of up to eight hexadecimal characters. The hexadecimal characters are parsed from most significant to least significant using fromHexDigit(int) to form an unsigned value. The value is zero extended to 32 bits and is returned as an int.
API Note:
Integer.parseInt(s, 16) and Integer.parseUnsignedInt(s, 16) are similar but allow all Unicode hexadecimal digits defined by Character.digit(ch, 16). HexFormat uses only hexadecimal characters "0-9", "A-F" and "a-f". Signed hexadecimal strings can be parsed with Integer.parseInt(String, int).
Parameters:
string - a CharSequence containing up to eight hexadecimal characters
Returns:
the value parsed from the string
Throws:
IllegalArgumentException - if the string length is greater than eight (8) or if any of the characters is not a hexadecimal character

fromHexDigits

public static int fromHexDigits(CharSequence string, int fromIndex, int toIndex)
Returns the int value parsed from a string range of up to eight hexadecimal characters. The characters in the range fromIndex to toIndex, exclusive, are parsed from most significant to least significant using fromHexDigit(int) to form an unsigned value. The value is zero extended to 32 bits and is returned as an int.
API Note:
Integer.parseInt(s, 16) and Integer.parseUnsignedInt(s, 16) are similar but allow all Unicode hexadecimal digits defined by Character.digit(ch, 16). HexFormat uses only hexadecimal characters "0-9", "A-F" and "a-f". Signed hexadecimal strings can be parsed with Integer.parseInt(String, int).
Parameters:
string - a CharSequence containing the characters
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive.
Returns:
the value parsed from the string range
Throws:
IndexOutOfBoundsException - if the range is out of bounds for the CharSequence
IllegalArgumentException - if length of the range is greater than eight (8) or if any of the characters is not a hexadecimal character

fromHexDigitsToLong

public static long fromHexDigitsToLong(CharSequence string)
Returns the long value parsed from a string of up to sixteen hexadecimal characters. The hexadecimal characters are parsed from most significant to least significant using fromHexDigit(int) to form an unsigned value. The value is zero extended to 64 bits and is returned as a long.
API Note:
Long.parseLong(s, 16) and Long.parseUnsignedLong(s, 16) are similar but allow all Unicode hexadecimal digits defined by Character.digit(ch, 16). HexFormat uses only hexadecimal characters "0-9", "A-F" and "a-f". Signed hexadecimal strings can be parsed with Long.parseLong(String, int).
Parameters:
string - a CharSequence containing up to sixteen hexadecimal characters
Returns:
the value parsed from the string
Throws:
IllegalArgumentException - if the string length is greater than sixteen (16) or if any of the characters is not a hexadecimal character

fromHexDigitsToLong

public static long fromHexDigitsToLong(CharSequence string, int fromIndex, int toIndex)
Returns the long value parsed from a string range of up to sixteen hexadecimal characters. The characters in the range fromIndex to toIndex, exclusive, are parsed from most significant to least significant using fromHexDigit(int) to form an unsigned value. The value is zero extended to 64 bits and is returned as a long.
API Note:
Long.parseLong(s, 16) and Long.parseUnsignedLong(s, 16) are similar but allow all Unicode hexadecimal digits defined by Character.digit(ch, 16). HexFormat uses only hexadecimal characters "0-9", "A-F" and "a-f". Signed hexadecimal strings can be parsed with Long.parseLong(String, int).
Parameters:
string - a CharSequence containing the characters
fromIndex - the initial index of the range, inclusive
toIndex - the final index of the range, exclusive.
Returns:
the value parsed from the string range
Throws:
IndexOutOfBoundsException - if the range is out of bounds for the CharSequence
IllegalArgumentException - if the length of the range is greater than sixteen (16) or if any of the characters is not a hexadecimal character

equals

public boolean equals(Object o)
Returns true if the other object is a HexFormat with the same parameters.
Overrides:
equals in class Object
Parameters:
o - an object, may be null
Returns:
true if the other object is a HexFormat and the parameters uppercase, delimiter, prefix, and suffix are equal; otherwise false
See Also:

hashCode

public int hashCode()
Returns a hashcode for this HexFormat.
Overrides:
hashCode in class Object
Returns:
a hashcode for this HexFormat
See Also:

toString

public String toString()
Returns a description of the formatter parameters for uppercase, delimiter, prefix, and suffix.
Overrides:
toString in class Object
Returns:
a description of this HexFormat

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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/HexFormat.html