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/* |
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* Written by Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/licenses/publicdomain. |
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* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
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*/ |
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package java.util; |
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import java.io.*; |
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class ArrayDeque<E> extends AbstractCollection<E> |
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implements Deque<E>, Cloneable, Serializable |
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implements Deque<E>, Cloneable, java.io.Serializable |
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{ |
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/** |
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* The array in which the elements of the deque are stored. |
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* other. We also guarantee that all array cells not holding |
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* deque elements are always null. |
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*/ |
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private transient E[] elements; |
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private transient Object[] elements; |
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/** |
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* The index of the element at the head of the deque (which is the |
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if (initialCapacity < 0) // Too many elements, must back off |
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initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
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} |
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elements = (E[]) new Object[initialCapacity]; |
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elements = new Object[initialCapacity]; |
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} |
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/** |
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Object[] a = new Object[newCapacity]; |
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System.arraycopy(elements, p, a, 0, r); |
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System.arraycopy(elements, 0, a, r, p); |
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elements = (E[])a; |
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elements = a; |
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head = 0; |
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tail = n; |
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} |
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* sufficient to hold 16 elements. |
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*/ |
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public ArrayDeque() { |
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elements = (E[]) new Object[16]; |
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elements = new Object[16]; |
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} |
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/** |
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public E pollFirst() { |
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int h = head; |
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E result = elements[h]; // Element is null if deque empty |
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@SuppressWarnings("unchecked") E result = (E) elements[h]; |
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// Element is null if deque empty |
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if (result == null) |
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return null; |
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elements[h] = null; // Must null out slot |
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public E pollLast() { |
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int t = (tail - 1) & (elements.length - 1); |
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E result = elements[t]; |
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@SuppressWarnings("unchecked") E result = (E) elements[t]; |
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if (result == null) |
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return null; |
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elements[t] = null; |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E getFirst() { |
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E x = elements[head]; |
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if (x == null) |
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@SuppressWarnings("unchecked") E result = (E) elements[head]; |
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if (result == null) |
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throw new NoSuchElementException(); |
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return x; |
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return result; |
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} |
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E getLast() { |
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E x = elements[(tail - 1) & (elements.length - 1)]; |
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if (x == null) |
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@SuppressWarnings("unchecked") |
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E result = (E) elements[(tail - 1) & (elements.length - 1)]; |
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if (result == null) |
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throw new NoSuchElementException(); |
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return x; |
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return result; |
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} |
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@SuppressWarnings("unchecked") |
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public E peekFirst() { |
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return elements[head]; // elements[head] is null if deque empty |
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// elements[head] is null if deque empty |
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return (E) elements[head]; |
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} |
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@SuppressWarnings("unchecked") |
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public E peekLast() { |
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return elements[(tail - 1) & (elements.length - 1)]; |
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return (E) elements[(tail - 1) & (elements.length - 1)]; |
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} |
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/** |
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return false; |
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int mask = elements.length - 1; |
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int i = head; |
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E x; |
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Object x; |
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while ( (x = elements[i]) != null) { |
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if (o.equals(x)) { |
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delete(i); |
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return false; |
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int mask = elements.length - 1; |
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int i = (tail - 1) & mask; |
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E x; |
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Object x; |
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while ( (x = elements[i]) != null) { |
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if (o.equals(x)) { |
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delete(i); |
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*/ |
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private boolean delete(int i) { |
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checkInvariants(); |
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final E[] elements = this.elements; |
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final Object[] elements = this.elements; |
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final int mask = elements.length - 1; |
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final int h = head; |
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final int t = tail; |
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public E next() { |
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if (cursor == fence) |
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throw new NoSuchElementException(); |
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E result = elements[cursor]; |
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@SuppressWarnings("unchecked") E result = (E) elements[cursor]; |
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// This check doesn't catch all possible comodifications, |
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// but does catch the ones that corrupt traversal |
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if (tail != fence || result == null) |
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if (cursor == fence) |
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throw new NoSuchElementException(); |
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cursor = (cursor - 1) & (elements.length - 1); |
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E result = elements[cursor]; |
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@SuppressWarnings("unchecked") E result = (E) elements[cursor]; |
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if (head != fence || result == null) |
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throw new ConcurrentModificationException(); |
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lastRet = cursor; |
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return false; |
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int mask = elements.length - 1; |
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int i = head; |
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E x; |
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Object x; |
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while ( (x = elements[i]) != null) { |
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if (o.equals(x)) |
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return true; |
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* The following code can be used to dump the deque into a newly |
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* allocated array of <tt>String</tt>: |
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* |
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* <pre> |
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* String[] y = x.toArray(new String[0]);</pre> |
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* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
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* |
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* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
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* <tt>toArray()</tt>. |
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* this deque |
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* @throws NullPointerException if the specified array is null |
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*/ |
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@SuppressWarnings("unchecked") |
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public <T> T[] toArray(T[] a) { |
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int size = size(); |
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if (a.length < size) |
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*/ |
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public ArrayDeque<E> clone() { |
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try { |
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@SuppressWarnings("unchecked") |
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ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
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result.elements = Arrays.copyOf(elements, elements.length); |
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return result; |
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* followed by all of its elements (each an object reference) in |
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* first-to-last order. |
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*/ |
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private void writeObject(ObjectOutputStream s) throws IOException { |
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private void writeObject(java.io.ObjectOutputStream s) |
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throws java.io.IOException { |
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s.defaultWriteObject(); |
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// Write out size |
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/** |
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* Deserialize this deque. |
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*/ |
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private void readObject(ObjectInputStream s) |
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throws IOException, ClassNotFoundException { |
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private void readObject(java.io.ObjectInputStream s) |
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throws java.io.IOException, ClassNotFoundException { |
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s.defaultReadObject(); |
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// Read in size and allocate array |
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// Read in all elements in the proper order. |
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for (int i = 0; i < size; i++) |
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elements[i] = (E)s.readObject(); |
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elements[i] = s.readObject(); |
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} |
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} |