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.
+ *
+ *