com.google.common.primitives
Class Ints

java.lang.Object
  com.google.common.primitives.Ints

@GwtCompatible(emulated=true)
public final class Ints
extends Object

Static utility methods pertaining to int primitives, that are not already found in either Integer or Arrays.

See the Guava User Guide article on primitive utilities.

Since:

1.0

Author:

Kevin Bourrillion

Field Summary

static int	BYTES The number of bytes required to represent a primitive int value.
static int	MAX_POWER_OF_TWO The largest power of two that can be represented as an int.

Method Summary

static List<Integer>	asList(int... backingArray) Returns a fixed-size list backed by the specified array, similar to Arrays.asList(Object[]).
static int	checkedCast(long value) Returns the int value that is equal to value, if possible.
static int	compare(int a, int b) Compares the two specified int values.
static int[]	concat(int[]... arrays) Returns the values from each provided array combined into a single array.
static boolean	contains(int[] array, int target) Returns true if target is present as an element anywhere in array.
static int[]	ensureCapacity(int[] array, int minLength, int padding) Returns an array containing the same values as array, but guaranteed to be of a specified minimum length.
static int	fromByteArray(byte[] bytes) Returns the int value whose big-endian representation is stored in the first 4 bytes of bytes; equivalent to ByteBuffer.wrap(bytes).getInt().
static int	fromBytes(byte b1, byte b2, byte b3, byte b4) Returns the int value whose byte representation is the given 4 bytes, in big-endian order; equivalent to Ints.fromByteArray(new byte[] {b1, b2, b3, b4}).
static int	hashCode(int value) Returns a hash code for value; equal to the result of invoking ((Integer) value).hashCode().
static int	indexOf(int[] array, int target) Returns the index of the first appearance of the value target in array.
static int	indexOf(int[] array, int[] target) Returns the start position of the first occurrence of the specified target within array, or -1 if there is no such occurrence.
static String	join(String separator, int... array) Returns a string containing the supplied int values separated by separator.
static int	lastIndexOf(int[] array, int target) Returns the index of the last appearance of the value target in array.
static Comparator<int[]>	lexicographicalComparator() Returns a comparator that compares two int arrays lexicographically.
static int	max(int... array) Returns the greatest value present in array.
static int	min(int... array) Returns the least value present in array.
static int	saturatedCast(long value) Returns the int nearest in value to value.
static int[]	toArray(Collection<? extends Number> collection) Returns an array containing each value of collection, converted to a int value in the manner of Number.intValue().
static byte[]	toByteArray(int value) Returns a big-endian representation of value in a 4-element byte array; equivalent to ByteBuffer.allocate(4).putInt(value).array().
static Integer	tryParse(String string) Parses the specified string as a signed decimal integer value.

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 int value.

See Also:

Constant Field Values

MAX_POWER_OF_TWO

public static final int MAX_POWER_OF_TWO

The largest power of two that can be represented as an int.

Since:

10.0

See Also:

Constant Field Values

Method Detail

hashCode

public static int hashCode(int value)

Returns a hash code for value; equal to the result of invoking ((Integer) value).hashCode().

Parameters:

value - a primitive int value

Returns:

a hash code for the value

checkedCast

public static int checkedCast(long value)

Returns the int value that is equal to value, if possible.

Parameters:

value - any value in the range of the int type

Returns:

the int value that equals value

Throws:

IllegalArgumentException - if value is greater than Integer.MAX_VALUE or less than Integer.MIN_VALUE

saturatedCast

public static int saturatedCast(long value)

Returns the int nearest in value to value.

Parameters:

value - any long value

Returns:

the same value cast to int if it is in the range of the int type, Integer.MAX_VALUE if it is too large, or Integer.MIN_VALUE if it is too small

compare

public static int compare(int a,
                          int b)

Compares the two specified int values. The sign of the value returned is the same as that of ((Integer) a).compareTo(b).

Parameters:

a - the first int to compare

b - the second int 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(int[] array,
                               int target)

Returns true if target is present as an element anywhere in array.

Parameters:

array - an array of int values, possibly empty

target - a primitive int value

Returns:

true if array[i] == target for some value of i

indexOf

public static int indexOf(int[] array,
                          int target)

Returns the index of the first appearance of the value target in array.

Parameters:

array - an array of int values, possibly empty

target - a primitive int value

Returns:

the least index i for which array[i] == target, or -1 if no such index exists.

indexOf

public static int indexOf(int[] array,
                          int[] 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 java.util.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(int[] array,
                              int target)

Returns the index of the last appearance of the value target in array.

Parameters:

array - an array of int values, possibly empty

target - a primitive int value

Returns:

the greatest index i for which array[i] == target, or -1 if no such index exists.

min

public static int min(int... array)

Returns the least value present in array.

Parameters:

array - a nonempty array of int values

Returns:

the value present in array that is less than or equal to every other value in the array

Throws:

IllegalArgumentException - if array is empty

max

public static int max(int... array)

Returns the greatest value present in array.

Parameters:

array - a nonempty array of int values

Returns:

the value present in array that is greater than or equal to every other value in the array

Throws:

IllegalArgumentException - if array is empty

concat

public static int[] concat(int[]... arrays)

Returns the values from each provided array combined into a single array. For example, concat(new int[] {a, b}, new int[] {}, new int[] {c} returns the array {a, b, c}.

Parameters:

arrays - zero or more int arrays

Returns:

a single array containing all the values from the source arrays, in order

toByteArray

@GwtIncompatible(value="doesn\'t work")
public static byte[] toByteArray(int value)

Returns a big-endian representation of value in a 4-element byte array; equivalent to ByteBuffer.allocate(4).putInt(value).array(). For example, the input value 0x12131415 would yield the byte array {0x12, 0x13, 0x14, 0x15}.

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

@GwtIncompatible(value="doesn\'t work")
public static int fromByteArray(byte[] bytes)

Returns the int value whose big-endian representation is stored in the first 4 bytes of bytes; equivalent to ByteBuffer.wrap(bytes).getInt(). For example, the input byte array {0x12, 0x13, 0x14, 0x15, 0x33} would yield the int value 0x12131415.

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

Throws:

IllegalArgumentException - if bytes has fewer than 4 elements

fromBytes

@GwtIncompatible(value="doesn\'t work")
public static int fromBytes(byte b1,
                                                 byte b2,
                                                 byte b3,
                                                 byte b4)

Returns the int value whose byte representation is the given 4 bytes, in big-endian order; equivalent to Ints.fromByteArray(new byte[] {b1, b2, b3, b4}).

Since:

7.0

ensureCapacity

public static int[] ensureCapacity(int[] 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:

IllegalArgumentException - if minLength or padding is negative

join

public static String join(String separator,
                          int... array)

Returns a string containing the supplied int values separated by separator. For example, join("-", 1, 2, 3) 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 int values, possibly empty

lexicographicalComparator

public static Comparator<int[]> lexicographicalComparator()

Returns a comparator that compares two int arrays lexicographically. That is, it compares, using compare(int, int)), 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, [] < [1] < [1, 2] < [2].

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

Since:

2.0

See Also:

Lexicographical order article at Wikipedia

toArray

public static int[] toArray(Collection<? extends Number> collection)

Returns an array containing each value of collection, converted to a int value in the manner of Number.intValue().

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:

NullPointerException - if collection or any of its elements is null

Since:

1.0 (parameter was Collection<Integer> before 12.0)

asList

public static List<Integer> asList(int... 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 Integer objects written to or read from it. For example, whether list.get(0) == list.get(0) is true for the returned list is unspecified.

Parameters:

backingArray - the array to back the list

Returns:

a list view of the array

tryParse

@Beta
@CheckForNull
@GwtIncompatible(value="TODO")
public static Integer tryParse(String string)

Parses the specified string as a signed decimal integer value. The ASCII character '-' ('\u002D') is recognized as the minus sign.

Unlike Integer.parseInt(String), this method returns null instead of throwing an exception if parsing fails.

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

Parameters:

string - the string representation of an integer value

Returns:

the integer value represented by string, or null if string has a length of zero or cannot be parsed as an integer value

Since:

11.0