Package it.unimi.dsi.fastutil.objects

Class ReferenceArrayList<K>

  • All Implemented Interfaces:
    ObjectIterable<K>, ReferenceCollection<K>, ReferenceList<K>, Stack<K>, Serializable, Cloneable, Iterable<K>, Collection<K>, List<K>, RandomAccess
    public class ReferenceArrayList<K>
extends AbstractReferenceList<K>
implements RandomAccess, Cloneable, Serializable
    A type-specific array-based list; provides some additional methods that use polymorphism to avoid (un)boxing.

    This class implements a lightweight, fast, open, optimized, reuse-oriented version of array-based lists. Instances of this class represent a list with an array that is enlarged as needed when new entries are created (by doubling the current length), but is never made smaller (even on a clear()). A family of trimming methods lets you control the size of the backing array; this is particularly useful if you reuse instances of this class. Range checks are equivalent to those of java.util's classes, but they are delayed as much as possible.

    The backing array is exposed by the elements() method. If an instance of this class was created by wrapping, backing-array reallocations will be performed using reflection, so that elements() can return an array of the same type of the original array: the comments about efficiency made in ObjectArrays apply here. Moreover, you must take into consideration that assignment to an array not of type Object[] is slower due to type checking.

    This class implements the bulk methods removeElements(), addElements() and getElements() using high-performance system calls (e.g., System.arraycopy() instead of expensive loops.

    See Also:
    ArrayList, Serialized Form

    • Field Detail

      • DEFAULT_INITIAL_CAPACITY

        public static final int DEFAULT_INITIAL_CAPACITY
        The initial default capacity of an array list.
        See Also:
        Constant Field Values

    • Constructor Detail

      • ReferenceArrayList

        public ReferenceArrayList​(int capacity)
        Creates a new array list with given capacity.
        Parameters:
        capacity - the initial capacity of the array list (may be 0).

      • ReferenceArrayList

        public ReferenceArrayList​(Collection<? extends K> c)
        Creates a new array list and fills it with a given collection.
        Parameters:
        c - a collection that will be used to fill the array list.

      • ReferenceArrayList

        public ReferenceArrayList​(ReferenceCollection<? extends K> c)
        Creates a new array list and fills it with a given type-specific collection.
        Parameters:
        c - a type-specific collection that will be used to fill the array list.

      • ReferenceArrayList

        public ReferenceArrayList​(ReferenceList<? extends K> l)
        Creates a new array list and fills it with a given type-specific list.
        Parameters:
        l - a type-specific list that will be used to fill the array list.

      • ReferenceArrayList

        public ReferenceArrayList​(K[] a)
        Creates a new array list and fills it with the elements of a given array.
        Parameters:
        a - an array whose elements will be used to fill the array list.

      • ReferenceArrayList

        public ReferenceArrayList​(K[] a,
                          int offset,
                          int length)
        Creates a new array list and fills it with the elements of a given array.
        Parameters:
        a - an array whose elements will be used to fill the array list.
        offset - the first element to use.
        length - the number of elements to use.

      • ReferenceArrayList

        public ReferenceArrayList​(Iterator<? extends K> i)
        Creates a new array list and fills it with the elements returned by an iterator..
        Parameters:
        i - an iterator whose returned elements will fill the array list.

      • ReferenceArrayList

        public ReferenceArrayList​(ObjectIterator<? extends K> i)
        Creates a new array list and fills it with the elements returned by a type-specific iterator..
        Parameters:
        i - a type-specific iterator whose returned elements will fill the array list.

    • Method Detail

      • elements

        public K[] elements()
        Returns the backing array of this list.

        If this array list was created by wrapping a given array, it is guaranteed that the type of the returned array will be the same. Otherwise, the returned array will be of type Object[] (in spite of the declared return type).

        Warning: This behaviour may cause (unfathomable) run-time errors if a method expects an array actually of type K[], but this methods returns an array of type Object[].

        Returns:
        the backing array.

      • wrap

        public static <K> ReferenceArrayList<K> wrap​(K[] a,
                                             int length)
        Wraps a given array into an array list of given size.

        Note it is guaranteed that the type of the array returned by elements() will be the same (see the comments in the class documentation).

        Parameters:
        a - an array to wrap.
        length - the length of the resulting array list.
        Returns:
        a new array list of the given size, wrapping the given array.

      • wrap

        public static <K> ReferenceArrayList<K> wrap​(K[] a)
        Wraps a given array into an array list.

        Note it is guaranteed that the type of the array returned by elements() will be the same (see the comments in the class documentation).

        Parameters:
        a - an array to wrap.
        Returns:
        a new array list wrapping the given array.

      • ensureCapacity

        public void ensureCapacity​(int capacity)
        Ensures that this array list can contain the given number of entries without resizing.
        Parameters:
        capacity - the new minimum capacity for this array list.

      • get

        public K get​(int index)
        Specified by:
        get in interface List<K>

      • size

        public void size​(int size)
        Description copied from interface: ReferenceList
        Sets the size of this list.

        If the specified size is smaller than the current size, the last elements are discarded. Otherwise, they are filled with 0/null/false.

        Specified by:
        size in interface ReferenceList<K>
        Overrides:
        size in class AbstractReferenceList<K>
        Parameters:
        size - the new size.

      • trim

        public void trim()
        Trims this array list so that the capacity is equal to the size.
        See Also:
        ArrayList.trimToSize()

      • trim

        public void trim​(int n)
        Trims the backing array if it is too large. If the current array length is smaller than or equal to n, this method does nothing. Otherwise, it trims the array length to the maximum between n and size().

        This method is useful when reusing lists. Clearing a list leaves the array length untouched. If you are reusing a list many times, you can call this method with a typical size to avoid keeping around a very large array just because of a few large transient lists.

        Parameters:
        n - the threshold for the trimming.

      • getElements

        public void getElements​(int from,
                        Object[] a,
                        int offset,
                        int length)
        Copies element of this type-specific list into the given array using optimized system calls.
        Specified by:
        getElements in interface ReferenceList<K>
        Overrides:
        getElements in class AbstractReferenceList<K>
        Parameters:
        from - the start index (inclusive).
        a - the destination array.
        offset - the offset into the destination array where to store the first element copied.
        length - the number of elements to be copied.

      • removeElements

        public void removeElements​(int from,
                           int to)
        Removes elements of this type-specific list using optimized system calls.
        Specified by:
        removeElements in interface ReferenceList<K>
        Overrides:
        removeElements in class AbstractReferenceList<K>
        Parameters:
        from - the start index (inclusive).
        to - the end index (exclusive).

      • addElements

        public void addElements​(int index,
                        K[] a,
                        int offset,
                        int length)
        Adds elements to this type-specific list using optimized system calls.
        Specified by:
        addElements in interface ReferenceList<K>
        Overrides:
        addElements in class AbstractReferenceList<K>
        Parameters:
        index - the index at which to add elements.
        a - the array containing the elements.
        offset - the offset of the first element to add.
        length - the number of elements to add.

      • equals

        public boolean equals​(ReferenceArrayList<K> l)
        Compares this type-specific array list to another one.

        This method exists only for sake of efficiency. The implementation inherited from the abstract implementation would already work.

        Parameters:
        l - a type-specific array list.
        Returns:
        true if the argument contains the same elements of this type-specific array list.