Package it.unimi.dsi.fastutil.ints

Class IntArrayList

java.lang.Object
java.util.AbstractCollection<Integer>
it.unimi.dsi.fastutil.ints.AbstractIntCollection
it.unimi.dsi.fastutil.ints.AbstractIntList
it.unimi.dsi.fastutil.ints.IntArrayList
All Implemented Interfaces:
IntCollection, IntIterable, IntList, IntStack, Stack<Integer>, Serializable, Cloneable, Comparable<List<? extends Integer>>, Iterable<Integer>, Collection<Integer>, List<Integer>, RandomAccess
public class IntArrayList
extends AbstractIntList
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 its 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.

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 Details

    • DEFAULT_INITIAL_CAPACITY

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

  • Constructor Details

    • IntArrayList

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

    • IntArrayList

      public IntArrayList()
      Creates a new array list with DEFAULT_INITIAL_CAPACITY capacity.

    • IntArrayList

      public IntArrayList​(Collection<? extends Integer> 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.

    • IntArrayList

      public IntArrayList​(IntCollection 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.

    • IntArrayList

      public IntArrayList​(IntList 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.

    • IntArrayList

      public IntArrayList​(int[] 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.

    • IntArrayList

      public IntArrayList​(int[] 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.

    • IntArrayList

      public IntArrayList​(Iterator<? extends Integer> 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.

    • IntArrayList

      public IntArrayList​(IntIterator 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 Details

    • elements

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

    • wrap

      public static IntArrayList wrap​(int[] 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 IntArrayList wrap​(int[] 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.

    • of

      @SafeVarargs public static IntArrayList of​(int... init)
      Creates an array list using a list of elements.
      Parameters:
      init - a list of elements that will be used to initialize the list.
      Returns:
      a new array list containing the given elements.

    • 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.

    • add

      public void add​(int index, int k)
      Description copied from class: AbstractIntList
      Inserts the specified element at the specified position in this list (optional operation).

      This implementation always throws an UnsupportedOperationException.

      Specified by:
      add in interface IntList
      Overrides:
      add in class AbstractIntList
      See Also:
      List.add(int,Object)

    • add

      public boolean add​(int k)
      Description copied from class: AbstractIntList
      Ensures that this collection contains the specified element (optional operation).

      This implementation always throws an UnsupportedOperationException.

      This implementation delegates to the type-specific version of List.add(int, Object).

      Specified by:
      add in interface IntCollection
      Specified by:
      add in interface IntList
      Overrides:
      add in class AbstractIntList
      See Also:
      Collection.add(Object)

    • getInt

      public int getInt​(int index)
      Description copied from interface: IntList
      Returns the element at the specified position in this list.
      Specified by:
      getInt in interface IntList
      See Also:
      List.get(int)

    • indexOf

      public int indexOf​(int k)
      Description copied from interface: IntList
      Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
      Specified by:
      indexOf in interface IntList
      Overrides:
      indexOf in class AbstractIntList
      See Also:
      List.indexOf(Object)

    • lastIndexOf

      public int lastIndexOf​(int k)
      Description copied from interface: IntList
      Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
      Specified by:
      lastIndexOf in interface IntList
      Overrides:
      lastIndexOf in class AbstractIntList
      See Also:
      List.lastIndexOf(Object)

    • removeInt

      public int removeInt​(int index)
      Description copied from class: AbstractIntList
      Removes the element at the specified position in this list (optional operation).

      This implementation always throws an UnsupportedOperationException.

      Specified by:
      removeInt in interface IntList
      Overrides:
      removeInt in class AbstractIntList
      See Also:
      List.remove(int)

    • rem

      public boolean rem​(int k)
      Description copied from class: AbstractIntList
      Removes a single instance of the specified element from this collection, if it is present (optional operation).

      This implementation delegates to indexOf().

      Specified by:
      rem in interface IntCollection
      Overrides:
      rem in class AbstractIntList
      See Also:
      List.remove(Object)

    • set

      public int set​(int index, int k)
      Description copied from class: AbstractIntList
      Replaces the element at the specified position in this list with the specified element (optional operation).

      This implementation always throws an UnsupportedOperationException.

      Specified by:
      set in interface IntList
      Overrides:
      set in class AbstractIntList
      See Also:
      List.set(int,Object)

    • clear

      public void clear()
      Description copied from class: AbstractIntList

      This implementation delegates to AbstractIntList.removeElements(int, int).

      Specified by:
      clear in interface Collection<Integer>
      Specified by:
      clear in interface List<Integer>
      Overrides:
      clear in class AbstractIntList

    • size

      public int size()
      Specified by:
      size in interface Collection<Integer>
      Specified by:
      size in interface List<Integer>
      Specified by:
      size in class AbstractCollection<Integer>

    • size

      public void size​(int size)
      Description copied from interface: IntList
      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 IntList
      Overrides:
      size in class AbstractIntList
      Parameters:
      size - the new size.

    • isEmpty

      public boolean isEmpty()
      Description copied from interface: Stack
      Checks whether the stack is empty.
      Specified by:
      isEmpty in interface Collection<Integer>
      Specified by:
      isEmpty in interface List<Integer>
      Specified by:
      isEmpty in interface Stack<Integer>
      Overrides:
      isEmpty in class AbstractCollection<Integer>
      Returns:
      true if the stack is empty.

    • 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, int[] 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 IntList
      Overrides:
      getElements in class AbstractIntList
      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 IntList
      Overrides:
      removeElements in class AbstractIntList
      Parameters:
      from - the start index (inclusive).
      to - the end index (exclusive).

    • addElements

      public void addElements​(int index, int[] a, int offset, int length)
      Adds elements to this type-specific list using optimized system calls.
      Specified by:
      addElements in interface IntList
      Overrides:
      addElements in class AbstractIntList
      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.

    • setElements

      public void setElements​(int index, int[] a, int offset, int length)
      Sets elements to this type-specific list using optimized system calls.
      Specified by:
      setElements in interface IntList
      Parameters:
      index - the index at which to start setting elements.
      a - the array containing the elements.
      offset - the offset of the first element to add.
      length - the number of elements to add.

    • toArray

      public int[] toArray​(int[] a)
      Description copied from interface: IntCollection
      Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.

      Note that, contrarily to Collection.toArray(Object[]), this methods just writes all elements of this collection: no special value will be added after the last one.

      Specified by:
      toArray in interface IntCollection
      Overrides:
      toArray in class AbstractIntCollection
      Parameters:
      a - if this array is big enough, it will be used to store this collection.
      Returns:
      a primitive type array containing the items of this collection.
      See Also:
      Collection.toArray(Object[])

    • addAll

      public boolean addAll​(int index, IntCollection c)
      Description copied from interface: IntList
      Inserts all of the elements in the specified type-specific collection into this type-specific list at the specified position (optional operation).
      Specified by:
      addAll in interface IntList
      Overrides:
      addAll in class AbstractIntList
      See Also:
      List.addAll(int,java.util.Collection)

    • addAll

      public boolean addAll​(int index, IntList l)
      Description copied from class: AbstractIntList
      Inserts all of the elements in the specified type-specific list into this type-specific list at the specified position (optional operation).

      This implementation delegates to the type-specific version of List.addAll(int, Collection).

      Specified by:
      addAll in interface IntList
      Overrides:
      addAll in class AbstractIntList
      See Also:
      List.add(int,Object)

    • removeAll

      public boolean removeAll​(IntCollection c)
      Description copied from interface: IntCollection
      Remove from this collection all elements in the given type-specific collection.
      Specified by:
      removeAll in interface IntCollection
      Overrides:
      removeAll in class AbstractIntCollection
      Parameters:
      c - a type-specific collection.
      Returns:
      true if this collection changed as a result of the call.
      See Also:
      Collection.removeAll(Collection)

    • removeAll

      public boolean removeAll​(Collection<?> c)
      Description copied from class: AbstractIntCollection

      This implementation delegates to the type-specific version if given a type-specific collection, otherwise is uses the implementation from AbstractCollection.

      Specified by:
      removeAll in interface Collection<Integer>
      Specified by:
      removeAll in interface List<Integer>
      Overrides:
      removeAll in class AbstractIntCollection

    • listIterator

      public IntListIterator listIterator​(int index)
      Description copied from class: AbstractIntList
      Returns a type-specific list iterator on the list starting at a given index.

      This implementation is based on the random-access methods.

      Specified by:
      listIterator in interface IntList
      Specified by:
      listIterator in interface List<Integer>
      Overrides:
      listIterator in class AbstractIntList
      See Also:
      List.listIterator(int)

    • sort

      public void sort​(IntComparator comp)
      Description copied from interface: IntList
      Sort a list using a type-specific comparator.

      Pass null to sort using natural ordering.

      Specified by:
      sort in interface IntList
      See Also:
      List.sort(java.util.Comparator)

    • unstableSort

      public void unstableSort​(IntComparator comp)
      Description copied from interface: IntList
      Sorts this list using a sort not assured to be stable.

      Pass null to sort using natural ordering.

      This differs from List.sort(java.util.Comparator) in that the results are not assured to be stable, but may be a bit faster.

      Unless a subclass specifies otherwise, the results of the method if the list is concurrently modified during the sort are unspecified.

      Specified by:
      unstableSort in interface IntList

    • clone

      public IntArrayList clone()

    • equals

      public boolean equals​(IntArrayList 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.

    • compareTo

      public int compareTo​(IntArrayList l)
      Compares this array list to another array list.

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

      Parameters:
      l - an array list.
      Returns:
      a negative integer, zero, or a positive integer as this list is lexicographically less than, equal to, or greater than the argument.