Class Longs


  • @GwtCompatible
    public final class Longs
    extends java.lang.Object
    Static utility methods pertaining to long primitives, that are not already found in either Long or Arrays.

    See the Guava User Guide article on primitive utilities.

    Since:
    1.0
    Author:
    Kevin Bourrillion
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int BYTES
      The number of bytes required to represent a primitive long value.
      static long MAX_POWER_OF_TWO
      The largest power of two that can be represented as a long.
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static java.util.List<java.lang.Long> asList​(long... backingArray)
      Returns a fixed-size list backed by the specified array, similar to Arrays.asList(Object[]).
      static int compare​(long a, long b)
      Compares the two specified long values.
      static long[] concat​(long[]... arrays)
      Returns the values from each provided array combined into a single array.
      static long constrainToRange​(long value, long min, long max)
      Returns the value nearest to value which is within the closed range [min..max].
      static boolean contains​(long[] array, long target)
      Returns true if target is present as an element anywhere in array.
      static long[] ensureCapacity​(long[] array, int minLength, int padding)
      Returns an array containing the same values as array, but guaranteed to be of a specified minimum length.
      static long fromByteArray​(byte[] bytes)
      Returns the long value whose big-endian representation is stored in the first 8 bytes of bytes; equivalent to ByteBuffer.wrap(bytes).getLong().
      static long fromBytes​(byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8)
      Returns the long value whose byte representation is the given 8 bytes, in big-endian order; equivalent to Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8}).
      static int hashCode​(long value)
      Returns a hash code for value; equal to the result of invoking ((Long) value).hashCode().
      static int indexOf​(long[] array, long target)
      Returns the index of the first appearance of the value target in array.
      static int indexOf​(long[] array, long[] target)
      Returns the start position of the first occurrence of the specified target within array, or -1 if there is no such occurrence.
      static java.lang.String join​(java.lang.String separator, long... array)
      Returns a string containing the supplied long values separated by separator.
      static int lastIndexOf​(long[] array, long target)
      Returns the index of the last appearance of the value target in array.
      static java.util.Comparator<long[]> lexicographicalComparator()
      Returns a comparator that compares two long arrays lexicographically.
      static long max​(long... array)
      Returns the greatest value present in array.
      static long min​(long... array)
      Returns the least value present in array.
      static void reverse​(long[] array)
      Reverses the elements of array.
      static void reverse​(long[] array, int fromIndex, int toIndex)
      Reverses the elements of array between fromIndex inclusive and toIndex exclusive.
      static void rotate​(long[] array, int distance)
      Performs a right rotation of array of "distance" places, so that the first element is moved to index "distance", and the element at index i ends up at index (distance + i) mod array.length.
      static void rotate​(long[] array, int distance, int fromIndex, int toIndex)
      Performs a right rotation of array between fromIndex inclusive and toIndex exclusive.
      static void sortDescending​(long[] array)
      Sorts the elements of array in descending order.
      static void sortDescending​(long[] array, int fromIndex, int toIndex)
      Sorts the elements of array between fromIndex inclusive and toIndex exclusive in descending order.
      static Converter<java.lang.String,​java.lang.Long> stringConverter()
      Returns a serializable converter object that converts between strings and longs using Long.decode(java.lang.String) and Long.toString().
      static long[] toArray​(java.util.Collection<? extends java.lang.Number> collection)
      Returns an array containing each value of collection, converted to a long value in the manner of Number.longValue().
      static byte[] toByteArray​(long value)
      Returns a big-endian representation of value in an 8-element byte array; equivalent to ByteBuffer.allocate(8).putLong(value).array().
      static java.lang.Long tryParse​(java.lang.String string)
      Parses the specified string as a signed decimal long value.
      static java.lang.Long tryParse​(java.lang.String string, int radix)
      Parses the specified string as a signed long value using the specified radix.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • BYTES

        public static final int BYTES
        The number of bytes required to represent a primitive long value.

        Java 8 users: use Long.BYTES instead.

        See Also:
        Constant Field Values
    • Method Detail

      • hashCode

        public static int hashCode​(long value)
        Returns a hash code for value; equal to the result of invoking ((Long) value).hashCode().

        This method always return the value specified by Long.hashCode() in java, which might be different from ((Long) value).hashCode() in GWT because Long.hashCode() in GWT does not obey the JRE contract.

        Java 8 users: use Long.hashCode(long) instead.

        Parameters:
        value - a primitive long value
        Returns:
        a hash code for the value
      • compare

        public static int compare​(long a,
                                  long b)
        Compares the two specified long values. The sign of the value returned is the same as that of ((Long) a).compareTo(b).

        Note for Java 7 and later: this method should be treated as deprecated; use the equivalent Long.compare(long, long) method instead.

        Parameters:
        a - the first long to compare
        b - the second long to compare
        Returns:
        a negative value if a is less than b; a positive value if a is greater than b; or zero if they are equal
      • contains

        public static boolean contains​(long[] array,
                                       long target)
        Returns true if target is present as an element anywhere in array.
        Parameters:
        array - an array of long values, possibly empty
        target - a primitive long value
        Returns:
        true if array[i] == target for some value of i
      • indexOf

        public static int indexOf​(long[] array,
                                  long target)
        Returns the index of the first appearance of the value target in array.
        Parameters:
        array - an array of long values, possibly empty
        target - a primitive long value
        Returns:
        the least index i for which array[i] == target, or -1 if no such index exists.
      • indexOf

        public static int indexOf​(long[] array,
                                  long[] target)
        Returns the start position of the first occurrence of the specified target within array, or -1 if there is no such occurrence.

        More formally, returns the lowest index i such that Arrays.copyOfRange(array, i, i + target.length) contains exactly the same elements as target.

        Parameters:
        array - the array to search for the sequence target
        target - the array to search for as a sub-sequence of array
      • lastIndexOf

        public static int lastIndexOf​(long[] array,
                                      long target)
        Returns the index of the last appearance of the value target in array.
        Parameters:
        array - an array of long values, possibly empty
        target - a primitive long value
        Returns:
        the greatest index i for which array[i] == target, or -1 if no such index exists.
      • min

        public static long min​(long... array)
        Returns the least value present in array.
        Parameters:
        array - a nonempty array of long values
        Returns:
        the value present in array that is less than or equal to every other value in the array
        Throws:
        java.lang.IllegalArgumentException - if array is empty
      • max

        public static long max​(long... array)
        Returns the greatest value present in array.
        Parameters:
        array - a nonempty array of long values
        Returns:
        the value present in array that is greater than or equal to every other value in the array
        Throws:
        java.lang.IllegalArgumentException - if array is empty
      • constrainToRange

        @Beta
        public static long constrainToRange​(long value,
                                            long min,
                                            long max)
        Returns the value nearest to value which is within the closed range [min..max].

        If value is within the range [min..max], value is returned unchanged. If value is less than min, min is returned, and if value is greater than max, max is returned.

        Parameters:
        value - the long value to constrain
        min - the lower bound (inclusive) of the range to constrain value to
        max - the upper bound (inclusive) of the range to constrain value to
        Throws:
        java.lang.IllegalArgumentException - if min > max
        Since:
        21.0
      • concat

        public static long[] concat​(long[]... arrays)
        Returns the values from each provided array combined into a single array. For example, concat(new long[] {a, b}, new long[] {}, new long[] {c} returns the array {a, b, c}.
        Parameters:
        arrays - zero or more long arrays
        Returns:
        a single array containing all the values from the source arrays, in order
      • toByteArray

        public static byte[] toByteArray​(long value)
        Returns a big-endian representation of value in an 8-element byte array; equivalent to ByteBuffer.allocate(8).putLong(value).array(). For example, the input value 0x1213141516171819L would yield the byte array {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}.

        If you need to convert and concatenate several values (possibly even of different types), use a shared ByteBuffer instance, or use ByteStreams.newDataOutput() to get a growable buffer.

      • fromByteArray

        public static long fromByteArray​(byte[] bytes)
        Returns the long value whose big-endian representation is stored in the first 8 bytes of bytes; equivalent to ByteBuffer.wrap(bytes).getLong(). For example, the input byte array {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19} would yield the long value 0x1213141516171819L.

        Arguably, it's preferable to use ByteBuffer; that library exposes much more flexibility at little cost in readability.

        Throws:
        java.lang.IllegalArgumentException - if bytes has fewer than 8 elements
      • fromBytes

        public static long fromBytes​(byte b1,
                                     byte b2,
                                     byte b3,
                                     byte b4,
                                     byte b5,
                                     byte b6,
                                     byte b7,
                                     byte b8)
        Returns the long value whose byte representation is the given 8 bytes, in big-endian order; equivalent to Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8}).
        Since:
        7.0
      • tryParse

        @Beta
        @CheckForNull
        public static java.lang.Long tryParse​(java.lang.String string)
        Parses the specified string as a signed decimal long value. The ASCII character '-' ( '\u002D') is recognized as the minus sign.

        Unlike Long.parseLong(String), this method returns null instead of throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns null if non-ASCII digits are present in the string.

        Note that strings prefixed with ASCII '+' are rejected, even under JDK 7, despite the change to Long.parseLong(String) for that version.

        Parameters:
        string - the string representation of a long value
        Returns:
        the long value represented by string, or null if string has a length of zero or cannot be parsed as a long value
        Throws:
        java.lang.NullPointerException - if string is null
        Since:
        14.0
      • tryParse

        @Beta
        @CheckForNull
        public static java.lang.Long tryParse​(java.lang.String string,
                                              int radix)
        Parses the specified string as a signed long value using the specified radix. The ASCII character '-' ('\u002D') is recognized as the minus sign.

        Unlike Long.parseLong(String, int), this method returns null instead of throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns null if non-ASCII digits are present in the string.

        Note that strings prefixed with ASCII '+' are rejected, even under JDK 7, despite the change to Long.parseLong(String, int) for that version.

        Parameters:
        string - the string representation of a long value
        radix - the radix to use when parsing
        Returns:
        the long value represented by string using radix, or null if string has a length of zero or cannot be parsed as a long value
        Throws:
        java.lang.IllegalArgumentException - if radix < Character.MIN_RADIX or radix > Character.MAX_RADIX
        java.lang.NullPointerException - if string is null
        Since:
        19.0
      • stringConverter

        @Beta
        public static Converter<java.lang.String,​java.lang.Long> stringConverter()
        Returns a serializable converter object that converts between strings and longs using Long.decode(java.lang.String) and Long.toString(). The returned converter throws NumberFormatException if the input string is invalid.

        Warning: please see Long.decode(java.lang.String) to understand exactly how strings are parsed. For example, the string "0123" is treated as octal and converted to the value 83L.

        Since:
        16.0
      • ensureCapacity

        public static long[] ensureCapacity​(long[] array,
                                            int minLength,
                                            int padding)
        Returns an array containing the same values as array, but guaranteed to be of a specified minimum length. If array already has a length of at least minLength, it is returned directly. Otherwise, a new array of size minLength + padding is returned, containing the values of array, and zeroes in the remaining places.
        Parameters:
        array - the source array
        minLength - the minimum length the returned array must guarantee
        padding - an extra amount to "grow" the array by if growth is necessary
        Returns:
        an array containing the values of array, with guaranteed minimum length minLength
        Throws:
        java.lang.IllegalArgumentException - if minLength or padding is negative
      • join

        public static java.lang.String join​(java.lang.String separator,
                                            long... array)
        Returns a string containing the supplied long values separated by separator. For example, join("-", 1L, 2L, 3L) returns the string "1-2-3".
        Parameters:
        separator - the text that should appear between consecutive values in the resulting string (but not at the start or end)
        array - an array of long values, possibly empty
      • lexicographicalComparator

        public static java.util.Comparator<long[]> lexicographicalComparator()
        Returns a comparator that compares two long arrays lexicographically. That is, it compares, using compare(long, long)), the first pair of values that follow any common prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For example, [] < [1L] < [1L, 2L] < [2L].

        The returned comparator is inconsistent with Object.equals(Object) (since arrays support only identity equality), but it is consistent with Arrays.equals(long[], long[]).

        Since:
        2.0
      • sortDescending

        public static void sortDescending​(long[] array)
        Sorts the elements of array in descending order.
        Since:
        23.1
      • sortDescending

        public static void sortDescending​(long[] array,
                                          int fromIndex,
                                          int toIndex)
        Sorts the elements of array between fromIndex inclusive and toIndex exclusive in descending order.
        Since:
        23.1
      • reverse

        public static void reverse​(long[] array)
        Reverses the elements of array. This is equivalent to Collections.reverse(Longs.asList(array)), but is likely to be more efficient.
        Since:
        23.1
      • reverse

        public static void reverse​(long[] array,
                                   int fromIndex,
                                   int toIndex)
        Reverses the elements of array between fromIndex inclusive and toIndex exclusive. This is equivalent to Collections.reverse(Longs.asList(array).subList(fromIndex, toIndex)), but is likely to be more efficient.
        Throws:
        java.lang.IndexOutOfBoundsException - if fromIndex < 0, toIndex > array.length, or toIndex > fromIndex
        Since:
        23.1
      • rotate

        public static void rotate​(long[] array,
                                  int distance)
        Performs a right rotation of array of "distance" places, so that the first element is moved to index "distance", and the element at index i ends up at index (distance + i) mod array.length. This is equivalent to Collections.rotate(Longs.asList(array), distance), but is considerably faster and avoids allocation and garbage collection.

        The provided "distance" may be negative, which will rotate left.

        Since:
        NEXT
      • rotate

        public static void rotate​(long[] array,
                                  int distance,
                                  int fromIndex,
                                  int toIndex)
        Performs a right rotation of array between fromIndex inclusive and toIndex exclusive. This is equivalent to Collections.rotate(Longs.asList(array).subList(fromIndex, toIndex), distance), but is considerably faster and avoids allocations and garbage collection.

        The provided "distance" may be negative, which will rotate left.

        Throws:
        java.lang.IndexOutOfBoundsException - if fromIndex < 0, toIndex > array.length, or toIndex > fromIndex
        Since:
        NEXT
      • toArray

        public static long[] toArray​(java.util.Collection<? extends java.lang.Number> collection)
        Returns an array containing each value of collection, converted to a long value in the manner of Number.longValue().

        Elements are copied from the argument collection as if by collection.toArray(). Calling this method is as thread-safe as calling that method.

        Parameters:
        collection - a collection of Number instances
        Returns:
        an array containing the same values as collection, in the same order, converted to primitives
        Throws:
        java.lang.NullPointerException - if collection or any of its elements is null
        Since:
        1.0 (parameter was Collection<Long> before 12.0)
      • asList

        public static java.util.List<java.lang.Long> asList​(long... backingArray)
        Returns a fixed-size list backed by the specified array, similar to Arrays.asList(Object[]). The list supports List.set(int, Object), but any attempt to set a value to null will result in a NullPointerException.

        The returned list maintains the values, but not the identities, of Long objects written to or read from it. For example, whether list.get(0) == list.get(0) is true for the returned list is unspecified.

        Note: when possible, you should represent your data as an ImmutableLongArray instead, which has an asList view.

        Parameters:
        backingArray - the array to back the list
        Returns:
        a list view of the array