Each vector tries to optimize storage management by maintaining a - * {@code capacity} and a {@code capacityIncrement}. The - * {@code capacity} is always at least as large as the vector - * size; it is usually larger because as components are added to the - * vector, the vector's storage increases in chunks the size of - * {@code capacityIncrement}. An application can increase the - * capacity of a vector before inserting a large number of - * components; this reduces the amount of incremental reallocation. - * - *
- * The iterators returned by this class's {@link #iterator() iterator} and - * {@link #listIterator(int) listIterator} methods are fail-fast: - * if the vector is structurally modified at any time after the iterator is - * created, in any way except through the iterator's own - * {@link ListIterator#remove() remove} or - * {@link ListIterator#add(Object) add} methods, the iterator will throw a - * {@link ConcurrentModificationException}. Thus, in the face of - * concurrent modification, the iterator fails quickly and cleanly, rather - * than risking arbitrary, non-deterministic behavior at an undetermined - * time in the future. The {@link Enumeration Enumerations} returned by - * the {@link #elements() elements} method are not fail-fast. - * - *
Note that the fail-fast behavior of an iterator cannot be guaranteed - * as it is, generally speaking, impossible to make any hard guarantees in the - * presence of unsynchronized concurrent modification. Fail-fast iterators - * throw {@code ConcurrentModificationException} on a best-effort basis. - * Therefore, it would be wrong to write a program that depended on this - * exception for its correctness: the fail-fast behavior of iterators - * should be used only to detect bugs. - * - *
As of the Java 2 platform v1.2, this class was retrofitted to
- * implement the {@link List} interface, making it a member of the
- *
- * Java Collections Framework. Unlike the new collection
- * implementations, {@code Vector} is synchronized. If a thread-safe
- * implementation is not needed, it is recommended to use {@link
- * ArrayList} in place of {@code Vector}.
- *
- * @author Lee Boynton
- * @author Jonathan Payne
- * @see Collection
- * @see LinkedList
- * @since JDK1.0
- */
-public class Vector Any array elements following the last element in the Vector are null.
- *
- * @serial
- */
- protected Object[] elementData;
-
- /**
- * The number of valid components in this {@code Vector} object.
- * Components {@code elementData[0]} through
- * {@code elementData[elementCount-1]} are the actual items.
- *
- * @serial
- */
- protected int elementCount;
-
- /**
- * The amount by which the capacity of the vector is automatically
- * incremented when its size becomes greater than its capacity. If
- * the capacity increment is less than or equal to zero, the capacity
- * of the vector is doubled each time it needs to grow.
- *
- * @serial
- */
- protected int capacityIncrement;
-
- /** use serialVersionUID from JDK 1.0.2 for interoperability */
- private static final long serialVersionUID = -2767605614048989439L;
-
- /**
- * Constructs an empty vector with the specified initial capacity and
- * capacity increment.
- *
- * @param initialCapacity the initial capacity of the vector
- * @param capacityIncrement the amount by which the capacity is
- * increased when the vector overflows
- * @throws IllegalArgumentException if the specified initial capacity
- * is negative
- */
- public Vector(int initialCapacity, int capacityIncrement) {
- super();
- if (initialCapacity < 0)
- throw new IllegalArgumentException("Illegal Capacity: "+
- initialCapacity);
- this.elementData = new Object[initialCapacity];
- this.capacityIncrement = capacityIncrement;
- }
-
- /**
- * Constructs an empty vector with the specified initial capacity and
- * with its capacity increment equal to zero.
- *
- * @param initialCapacity the initial capacity of the vector
- * @throws IllegalArgumentException if the specified initial capacity
- * is negative
- */
- public Vector(int initialCapacity) {
- this(initialCapacity, 0);
- }
-
- /**
- * Constructs an empty vector so that its internal data array
- * has size {@code 10} and its standard capacity increment is
- * zero.
- */
- public Vector() {
- this(10);
- }
-
- /**
- * Constructs a vector containing the elements of the specified
- * collection, in the order they are returned by the collection's
- * iterator.
- *
- * @param c the collection whose elements are to be placed into this
- * vector
- * @throws NullPointerException if the specified collection is null
- * @since 1.2
- */
- public Vector(Collection c) {
- elementData = c.toArray();
- elementCount = elementData.length;
- // c.toArray might (incorrectly) not return Object[] (see 6260652)
- if (elementData.getClass() != Object[].class)
- elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
- }
-
- /**
- * Copies the components of this vector into the specified array.
- * The item at index {@code k} in this vector is copied into
- * component {@code k} of {@code anArray}.
- *
- * @param anArray the array into which the components get copied
- * @throws NullPointerException if the given array is null
- * @throws IndexOutOfBoundsException if the specified array is not
- * large enough to hold all the components of this vector
- * @throws ArrayStoreException if a component of this vector is not of
- * a runtime type that can be stored in the specified array
- * @see #toArray(Object[])
- */
- public synchronized void copyInto(Object[] anArray) {
- System.arraycopy(elementData, 0, anArray, 0, elementCount);
- }
-
- /**
- * Trims the capacity of this vector to be the vector's current
- * size. If the capacity of this vector is larger than its current
- * size, then the capacity is changed to equal the size by replacing
- * its internal data array, kept in the field {@code elementData},
- * with a smaller one. An application can use this operation to
- * minimize the storage of a vector.
- */
- public synchronized void trimToSize() {
- modCount++;
- int oldCapacity = elementData.length;
- if (elementCount < oldCapacity) {
- elementData = Arrays.copyOf(elementData, elementCount);
- }
- }
-
- /**
- * Increases the capacity of this vector, if necessary, to ensure
- * that it can hold at least the number of components specified by
- * the minimum capacity argument.
- *
- * If the current capacity of this vector is less than
- * {@code minCapacity}, then its capacity is increased by replacing its
- * internal data array, kept in the field {@code elementData}, with a
- * larger one. The size of the new data array will be the old size plus
- * {@code capacityIncrement}, unless the value of
- * {@code capacityIncrement} is less than or equal to zero, in which case
- * the new capacity will be twice the old capacity; but if this new size
- * is still smaller than {@code minCapacity}, then the new capacity will
- * be {@code minCapacity}.
- *
- * @param minCapacity the desired minimum capacity
- */
- public synchronized void ensureCapacity(int minCapacity) {
- if (minCapacity > 0) {
- modCount++;
- ensureCapacityHelper(minCapacity);
- }
- }
-
- /**
- * This implements the unsynchronized semantics of ensureCapacity.
- * Synchronized methods in this class can internally call this
- * method for ensuring capacity without incurring the cost of an
- * extra synchronization.
- *
- * @see #ensureCapacity(int)
- */
- private void ensureCapacityHelper(int minCapacity) {
- // overflow-conscious code
- if (minCapacity - elementData.length > 0)
- grow(minCapacity);
- }
-
- /**
- * The maximum size of array to allocate.
- * Some VMs reserve some header words in an array.
- * Attempts to allocate larger arrays may result in
- * OutOfMemoryError: Requested array size exceeds VM limit
- */
- private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
-
- private void grow(int minCapacity) {
- // overflow-conscious code
- int oldCapacity = elementData.length;
- int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
- capacityIncrement : oldCapacity);
- if (newCapacity - minCapacity < 0)
- newCapacity = minCapacity;
- if (newCapacity - MAX_ARRAY_SIZE > 0)
- newCapacity = hugeCapacity(minCapacity);
- elementData = Arrays.copyOf(elementData, newCapacity);
- }
-
- private static int hugeCapacity(int minCapacity) {
- if (minCapacity < 0) // overflow
- throw new OutOfMemoryError();
- return (minCapacity > MAX_ARRAY_SIZE) ?
- Integer.MAX_VALUE :
- MAX_ARRAY_SIZE;
- }
-
- /**
- * Sets the size of this vector. If the new size is greater than the
- * current size, new {@code null} items are added to the end of
- * the vector. If the new size is less than the current size, all
- * components at index {@code newSize} and greater are discarded.
- *
- * @param newSize the new size of this vector
- * @throws ArrayIndexOutOfBoundsException if the new size is negative
- */
- public synchronized void setSize(int newSize) {
- modCount++;
- if (newSize > elementCount) {
- ensureCapacityHelper(newSize);
- } else {
- for (int i = newSize ; i < elementCount ; i++) {
- elementData[i] = null;
- }
- }
- elementCount = newSize;
- }
-
- /**
- * Returns the current capacity of this vector.
- *
- * @return the current capacity (the length of its internal
- * data array, kept in the field {@code elementData}
- * of this vector)
- */
- public synchronized int capacity() {
- return elementData.length;
- }
-
- /**
- * Returns the number of components in this vector.
- *
- * @return the number of components in this vector
- */
- public synchronized int size() {
- return elementCount;
- }
-
- /**
- * Tests if this vector has no components.
- *
- * @return {@code true} if and only if this vector has
- * no components, that is, its size is zero;
- * {@code false} otherwise.
- */
- public synchronized boolean isEmpty() {
- return elementCount == 0;
- }
-
- /**
- * Returns an enumeration of the components of this vector. The
- * returned {@code Enumeration} object will generate all items in
- * this vector. The first item generated is the item at index {@code 0},
- * then the item at index {@code 1}, and so on.
- *
- * @return an enumeration of the components of this vector
- * @see Iterator
- */
- public Enumeration This method is identical in functionality to the {@link #get(int)}
- * method (which is part of the {@link List} interface).
- *
- * @param index an index into this vector
- * @return the component at the specified index
- * @throws ArrayIndexOutOfBoundsException if the index is out of range
- * ({@code index < 0 || index >= size()})
- */
- public synchronized E elementAt(int index) {
- if (index >= elementCount) {
- throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
- }
-
- return elementData(index);
- }
-
- /**
- * Returns the first component (the item at index {@code 0}) of
- * this vector.
- *
- * @return the first component of this vector
- * @throws NoSuchElementException if this vector has no components
- */
- public synchronized E firstElement() {
- if (elementCount == 0) {
- throw new NoSuchElementException();
- }
- return elementData(0);
- }
-
- /**
- * Returns the last component of the vector.
- *
- * @return the last component of the vector, i.e., the component at index
- * The index must be a value greater than or equal to {@code 0}
- * and less than the current size of the vector.
- *
- * This method is identical in functionality to the
- * {@link #set(int, Object) set(int, E)}
- * method (which is part of the {@link List} interface). Note that the
- * {@code set} method reverses the order of the parameters, to more closely
- * match array usage. Note also that the {@code set} method returns the
- * old value that was stored at the specified position.
- *
- * @param obj what the component is to be set to
- * @param index the specified index
- * @throws ArrayIndexOutOfBoundsException if the index is out of range
- * ({@code index < 0 || index >= size()})
- */
- public synchronized void setElementAt(E obj, int index) {
- if (index >= elementCount) {
- throw new ArrayIndexOutOfBoundsException(index + " >= " +
- elementCount);
- }
- elementData[index] = obj;
- }
-
- /**
- * Deletes the component at the specified index. Each component in
- * this vector with an index greater or equal to the specified
- * {@code index} is shifted downward to have an index one
- * smaller than the value it had previously. The size of this vector
- * is decreased by {@code 1}.
- *
- * The index must be a value greater than or equal to {@code 0}
- * and less than the current size of the vector.
- *
- * This method is identical in functionality to the {@link #remove(int)}
- * method (which is part of the {@link List} interface). Note that the
- * {@code remove} method returns the old value that was stored at the
- * specified position.
- *
- * @param index the index of the object to remove
- * @throws ArrayIndexOutOfBoundsException if the index is out of range
- * ({@code index < 0 || index >= size()})
- */
- public synchronized void removeElementAt(int index) {
- modCount++;
- if (index >= elementCount) {
- throw new ArrayIndexOutOfBoundsException(index + " >= " +
- elementCount);
- }
- else if (index < 0) {
- throw new ArrayIndexOutOfBoundsException(index);
- }
- int j = elementCount - index - 1;
- if (j > 0) {
- System.arraycopy(elementData, index + 1, elementData, index, j);
- }
- elementCount--;
- elementData[elementCount] = null; /* to let gc do its work */
- }
-
- /**
- * Inserts the specified object as a component in this vector at the
- * specified {@code index}. Each component in this vector with
- * an index greater or equal to the specified {@code index} is
- * shifted upward to have an index one greater than the value it had
- * previously.
- *
- * The index must be a value greater than or equal to {@code 0}
- * and less than or equal to the current size of the vector. (If the
- * index is equal to the current size of the vector, the new element
- * is appended to the Vector.)
- *
- * This method is identical in functionality to the
- * {@link #add(int, Object) add(int, E)}
- * method (which is part of the {@link List} interface). Note that the
- * {@code add} method reverses the order of the parameters, to more closely
- * match array usage.
- *
- * @param obj the component to insert
- * @param index where to insert the new component
- * @throws ArrayIndexOutOfBoundsException if the index is out of range
- * ({@code index < 0 || index > size()})
- */
- public synchronized void insertElementAt(E obj, int index) {
- modCount++;
- if (index > elementCount) {
- throw new ArrayIndexOutOfBoundsException(index
- + " > " + elementCount);
- }
- ensureCapacityHelper(elementCount + 1);
- System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
- elementData[index] = obj;
- elementCount++;
- }
-
- /**
- * Adds the specified component to the end of this vector,
- * increasing its size by one. The capacity of this vector is
- * increased if its size becomes greater than its capacity.
- *
- * This method is identical in functionality to the
- * {@link #add(Object) add(E)}
- * method (which is part of the {@link List} interface).
- *
- * @param obj the component to be added
- */
- public synchronized void addElement(E obj) {
- modCount++;
- ensureCapacityHelper(elementCount + 1);
- elementData[elementCount++] = obj;
- }
-
- /**
- * Removes the first (lowest-indexed) occurrence of the argument
- * from this vector. If the object is found in this vector, each
- * component in the vector with an index greater or equal to the
- * object's index is shifted downward to have an index one smaller
- * than the value it had previously.
- *
- * This method is identical in functionality to the
- * {@link #remove(Object)} method (which is part of the
- * {@link List} interface).
- *
- * @param obj the component to be removed
- * @return {@code true} if the argument was a component of this
- * vector; {@code false} otherwise.
- */
- public synchronized boolean removeElement(Object obj) {
- modCount++;
- int i = indexOf(obj);
- if (i >= 0) {
- removeElementAt(i);
- return true;
- }
- return false;
- }
-
- /**
- * Removes all components from this vector and sets its size to zero.
- *
- * This method is identical in functionality to the {@link #clear}
- * method (which is part of the {@link List} interface).
- */
- public synchronized void removeAllElements() {
- modCount++;
- // Let gc do its work
- for (int i = 0; i < elementCount; i++)
- elementData[i] = null;
-
- elementCount = 0;
- }
-
- /**
- * Returns a clone of this vector. The copy will contain a
- * reference to a clone of the internal data array, not a reference
- * to the original internal data array of this {@code Vector} object.
- *
- * @return a clone of this vector
- */
- public synchronized Object clone() {
- try {
- @SuppressWarnings("unchecked")
- Vector If the Vector fits in the specified array with room to spare
- * (i.e., the array has more elements than the Vector),
- * the element in the array immediately following the end of the
- * Vector is set to null. (This is useful in determining the length
- * of the Vector only if the caller knows that the Vector
- * does not contain any null elements.)
- *
- * @param a the array into which the elements of the Vector are to
- * be stored, if it is big enough; otherwise, a new array of the
- * same runtime type is allocated for this purpose.
- * @return an array containing the elements of the Vector
- * @throws ArrayStoreException if the runtime type of a is not a supertype
- * of the runtime type of every element in this Vector
- * @throws NullPointerException if the given array is null
- * @since 1.2
- */
- @SuppressWarnings("unchecked")
- public synchronized This method eliminates the need for explicit range operations (of
- * the sort that commonly exist for arrays). Any operation that expects
- * a List can be used as a range operation by operating on a subList view
- * instead of a whole List. For example, the following idiom
- * removes a range of elements from a List:
- * The semantics of the List returned by this method become undefined if
- * the backing list (i.e., this List) is structurally modified in
- * any way other than via the returned List. (Structural modifications are
- * those that change the size of the List, or otherwise perturb it in such
- * a fashion that iterations in progress may yield incorrect results.)
- *
- * @param fromIndex low endpoint (inclusive) of the subList
- * @param toIndex high endpoint (exclusive) of the subList
- * @return a view of the specified range within this List
- * @throws IndexOutOfBoundsException if an endpoint index value is out of range
- * {@code (fromIndex < 0 || toIndex > size)}
- * @throws IllegalArgumentException if the endpoint indices are out of order
- * {@code (fromIndex > toIndex)}
- */
- public synchronized List The returned list iterator is fail-fast.
- *
- * @throws IndexOutOfBoundsException {@inheritDoc}
- */
- public synchronized ListIterator The returned list iterator is fail-fast.
- *
- * @see #listIterator(int)
- */
- public synchronized ListIterator The returned iterator is fail-fast.
- *
- * @return an iterator over the elements in this list in proper sequence
- */
- public synchronized Iteratorsize() - 1.
- * @throws NoSuchElementException if this vector is empty
- */
- public synchronized E lastElement() {
- if (elementCount == 0) {
- throw new NoSuchElementException();
- }
- return elementData(elementCount - 1);
- }
-
- /**
- * Sets the component at the specified {@code index} of this
- * vector to be the specified object. The previous component at that
- * position is discarded.
- *
- *
- * list.subList(from, to).clear();
- *
- * Similar idioms may be constructed for indexOf and lastIndexOf,
- * and all of the algorithms in the Collections class can be applied to
- * a subList.
- *
- *