Module java.base
Package java.util

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
    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.
    formatHex​(byte[] bytes)
    Returns a hexadecimal string formatted from a byte array.
    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
    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
    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
    Returns a hashcode for this HexFormat.
    static boolean
    isHexDigit​(int ch)
    Returns true if the character is a valid hexadecimal character or codepoint.
    boolean
    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[]
    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.
    Returns the prefix used for each hexadecimal value in formatted hexadecimal strings.
    Returns the suffix used for each hexadecimal value in formatted hexadecimal strings.
    toHexDigits​(byte value)
    Returns the two hexadecimal characters for the byte value.
    toHexDigits​(char value)
    Returns the four hexadecimal characters for the char value.
    toHexDigits​(int value)
    Returns the eight hexadecimal characters for the int value.
    toHexDigits​(long value)
    Returns the sixteen hexadecimal characters for the long value.
    toHexDigits​(long value, int digits)
    Returns up to sixteen hexadecimal characters for the long value.
    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.
    Returns a description of the formatter parameters for uppercase, delimiter, prefix, and suffix.
    withDelimiter​(String delimiter)
    Returns a copy of this HexFormat with the delimiter.
    Returns a copy of this HexFormat to use lowercase hexadecimal characters.
    withPrefix​(String prefix)
    Returns a copy of this HexFormat with the prefix.
    withSuffix​(String suffix)
    Returns a copy of this HexFormat with the suffix.
    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:
      Integer.toHexString(int)
    • 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:
      Long.toHexString(long)
    • 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:
      Object.hashCode(), HashMap
    • hashCode

      public int hashCode()
      Returns a hashcode for this HexFormat.
      Overrides:
      hashCode in class Object
      Returns:
      a hashcode for this HexFormat
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
    • 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