Package com.google.common.primitives

Class ImmutableIntArray

  • All Implemented Interfaces:
    Serializable
    @Beta
@GwtCompatible
@Immutable
public final class ImmutableIntArray
extends Object
implements Serializable
    An immutable array of int values, with an API resembling List.

    Advantages compared to int[]:

    • All the many well-known advantages of immutability (read Effective Java, third edition, Item 17).
    • Has the value-based (not identity-based) equals(java.lang.Object), hashCode(), and toString() behavior you expect.
    • Offers useful operations beyond just get and length, so you don't have to hunt through classes like Arrays and Ints for them.
    • Supports a copy-free subArray(int, int) view, so methods that accept this type don't need to add overloads that accept start and end indexes.
    • Can be streamed without "breaking the chain": foo.getBarInts().stream()....
    • Access to all collection-based utilities via asList() (though at the cost of allocating garbage).

    Disadvantages compared to int[]:

    • Memory footprint has a fixed overhead (about 24 bytes per instance).
    • Some construction use cases force the data to be copied (though several construction APIs are offered that don't).
    • Can't be passed directly to methods that expect int[] (though the most common utilities do have replacements here).
    • Dependency on com.google.common / Guava.

    Advantages compared to ImmutableList <Integer>:

    • Improved memory compactness and locality.
    • Can be queried without allocating garbage.
    • Access to IntStream features (like IntStream.sum()) using stream() instead of the awkward stream().mapToInt(v -> v).

    Disadvantages compared to ImmutableList<Integer>:

    • Can't be passed directly to methods that expect Iterable, Collection, or List (though the most common utilities do have replacements here, and there is a lazy asList() view).
    Since:
    22.0
    See Also:
    Serialized Form

    • Method Detail

      • of

        public static ImmutableIntArray of​(int e0)
        Returns an immutable array containing a single value.

      • of

        public static ImmutableIntArray of​(int e0,
                                   int e1)
        Returns an immutable array containing the given values, in order.

      • of

        public static ImmutableIntArray of​(int e0,
                                   int e1,
                                   int e2)
        Returns an immutable array containing the given values, in order.

      • of

        public static ImmutableIntArray of​(int e0,
                                   int e1,
                                   int e2,
                                   int e3)
        Returns an immutable array containing the given values, in order.

      • of

        public static ImmutableIntArray of​(int e0,
                                   int e1,
                                   int e2,
                                   int e3,
                                   int e4)
        Returns an immutable array containing the given values, in order.

      • of

        public static ImmutableIntArray of​(int e0,
                                   int e1,
                                   int e2,
                                   int e3,
                                   int e4,
                                   int e5)
        Returns an immutable array containing the given values, in order.

      • of

        public static ImmutableIntArray of​(int first,
                                   int... rest)
        Returns an immutable array containing the given values, in order.

        The array rest must not be longer than Integer.MAX_VALUE - 1.

      • copyOf

        public static ImmutableIntArray copyOf​(int[] values)
        Returns an immutable array containing the given values, in order.

      • builder

        public static ImmutableIntArray.Builder builder​(int initialCapacity)
        Returns a new, empty builder for ImmutableIntArray instances, sized to hold up to initialCapacity values without resizing. The returned builder is not thread-safe.

        Performance note: When feasible, initialCapacity should be the exact number of values that will be added, if that knowledge is readily available. It is better to guess a value slightly too high than slightly too low. If the value is not exact, the ImmutableIntArray that is built will very likely occupy more memory than strictly necessary; to trim memory usage, build using builder.build().trimmed().

      • builder

        public static ImmutableIntArray.Builder builder()
        Returns a new, empty builder for ImmutableIntArray instances, with a default initial capacity. The returned builder is not thread-safe.

        Performance note: The ImmutableIntArray that is built will very likely occupy more memory than necessary; to trim memory usage, build using builder.build().trimmed().

      • length

        public int length()
        Returns the number of values in this array.

      • isEmpty

        public boolean isEmpty()
        Returns true if there are no values in this array (length() is zero).

      • get

        public int get​(int index)
        Returns the int value present at the given index.
        Throws:
        IndexOutOfBoundsException - if index is negative, or greater than or equal to length()

      • indexOf

        public int indexOf​(int target)
        Returns the smallest index for which get(int) returns target, or -1 if no such index exists. Equivalent to asList().indexOf(target).

      • lastIndexOf

        public int lastIndexOf​(int target)
        Returns the largest index for which get(int) returns target, or -1 if no such index exists. Equivalent to asList().lastIndexOf(target).

      • contains

        public boolean contains​(int target)
        Returns true if target is present at any index in this array. Equivalent to asList().contains(target).

      • forEach

        public void forEach​(IntConsumer consumer)
        Invokes consumer for each value contained in this array, in order.

      • stream

        public IntStream stream()
        Returns a stream over the values in this array, in order.

      • toArray

        public int[] toArray()
        Returns a new, mutable copy of this array's values, as a primitive int[].

      • subArray

        public ImmutableIntArray subArray​(int startIndex,
                                  int endIndex)
        Returns a new immutable array containing the values in the specified range.

        Performance note: The returned array has the same full memory footprint as this one does (no actual copying is performed). To reduce memory usage, use subArray(start, end).trimmed().

      • asList

        public List<Integer> asList()
        Returns an immutable view of this array's values as a List; note that int values are boxed into Integer instances on demand, which can be very expensive. The returned list should be used once and discarded. For any usages beyond that, pass the returned list to ImmutableList.copyOf and use that list instead.

      • equals

        public boolean equals​(@CheckForNull
                      Object object)
        Returns true if object is an ImmutableIntArray containing the same values as this one, in the same order.
        Overrides:
        equals in class Object
        Parameters:
        object - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • trimmed

        public ImmutableIntArray trimmed()
        Returns an immutable array containing the same values as this array. This is logically a no-op, and in some circumstances this itself is returned. However, if this instance is a subArray(int, int) view of a larger array, this method will copy only the appropriate range of values, resulting in an equivalent array with a smaller memory footprint.