/* Vector.java -- Class that provides growable arrays.
Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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package java.util;
/**
* The <code>Vector</code> classes implements growable arrays of Objects. You
* can access elements in a Vector with an index, just as you can in a built in
* array, but Vectors can grow and shrink to accommodate more or fewer objects.
* <p>
*
* Vectors try to mantain efficiency in growing by having a
* <code>capacityIncrement</code> that can be specified at instantiation. When
* a Vector can no longer hold a new Object, it grows by the amount in
* <code>capacityIncrement</code>. If this value is 0, the vector doubles in
* size.
* <p>
*
* Vector implements the JDK 1.2 List interface, and is therefore a fully
* compliant Collection object. The iterators are fail-fast - if external code
* structurally modifies the vector, any operation on the iterator will then
* throw a {@link ConcurrentModificationException}. The Vector class is fully
* synchronized, but the iterators are not. So, when iterating over a vector, be
* sure to synchronize on the vector itself. If you don't want the expense of
* synchronization, use ArrayList instead. On the other hand, the Enumeration of
* elements() is not thread-safe, nor is it fail-fast; so it can lead to
* undefined behavior even in a single thread if you modify the vector during
* iteration.
* <p>
*
* Note: Some methods, especially those specified by List, specify throwing
* {@link IndexOutOfBoundsException}, but it is easier to implement by throwing
* the subclass {@link ArrayIndexOutOfBoundsException}. Others directly specify
* this subclass.
*
* @author Scott G. Miller
* @author Bryce McKinlay
* @author Eric Blake (ebb9@email.byu.edu)
* @see Collection
* @see List
* @see ArrayList
* @see LinkedList
* @since 1.0
* @status updated to 1.4
*/
public class Vector {
/**
* The internal array used to hold members of a Vector. The elements are in
* positions 0 through elementCount - 1, and all remaining slots are null.
*
* @serial the elements
*/
protected Object[] elementData;
/**
* The number of elements currently in the vector, also returned by
* {@link #size}.
*
* @serial the size
*/
protected int elementCount;
/**
* The amount the Vector's internal array should be increased in size when a
* new element is added that exceeds the current size of the array, or when
* {@link #ensureCapacity} is called. If <= 0, the vector just doubles in
* size.
*
* @serial the amount to grow the vector by
*/
protected int capacityIncrement;
/**
* A count of the number of structural modifications that have been made to
* the list (that is, insertions and removals).
*/
protected int modCount;
/**
* Constructs an empty vector with an initial size of 10, and a capacity
* increment of 0
*/
public Vector() {
this(10, 0);
}
/**
* Constructs a Vector with the initial capacity and capacity increment
* specified.
*
* @param initialCapacity
* the initial size of the Vector's internal array
* @param capacityIncrement
* the amount the internal array should be increased by when
* necessary, 0 to double the size
* @throws IllegalArgumentException
* if initialCapacity < 0
*/
public Vector(int initialCapacity, int capacityIncrement) {
if (initialCapacity < 0)
throw new IllegalArgumentException();
elementData = new Object[initialCapacity];
this.capacityIncrement = capacityIncrement;
modCount = 0;
}
/**
* Constructs a Vector with the initial capacity specified, and a capacity
* increment of 0 (double in size).
*
* @param initialCapacity
* the initial size of the Vector's internal array
* @throws IllegalArgumentException
* if initialCapacity < 0
*/
public Vector(int initialCapacity) {
this(initialCapacity, 0);
}
/**
* Adds an element to the Vector at the end of the Vector. The vector is
* increased by ensureCapacity(size() + 1) if needed.
*
* @param obj
* the object to add to the Vector
*/
public synchronized void addElement(Object obj) {
if (elementCount == elementData.length)
ensureCapacity(elementCount + 1);
modCount++;
elementData[elementCount++] = obj;
}
/**
* Returns the size of the internal data array (not the amount of elements
* contained in the Vector).
*
* @return capacity of the internal data array
*/
public synchronized int capacity() {
return elementData.length;
}
/**
* Returns true when <code>elem</code> is contained in this Vector.
*
* @param elem
* the element to check
* @return true if the object is contained in this Vector, false otherwise
*/
public boolean contains(Object elem) {
return indexOf(elem, 0) >= 0;
}
/**
* Copies the contents of the Vector into the provided array. If the array
* is too small to fit all the elements in the Vector, an
* {@link IndexOutOfBoundsException} is thrown without modifying the array.
* Old elements in the array are overwritten by the new elements.
*
* @param a
* target array for the copy
* @throws IndexOutOfBoundsException
* the array is not large enough
* @throws NullPointerException
* the array is null
* @see #toArray(Object[])
*/
public synchronized void copyInto(Object[] a) {
System.arraycopy(elementData, 0, a, 0, elementCount);
}
/**
* Returns the Object stored at <code>index</code>.
*
* @param index
* the index of the Object to retrieve
* @return the object at <code>index</code>
* @throws ArrayIndexOutOfBoundsException
* index < 0 || index >= size()
* @see #get(int)
*/
public synchronized Object elementAt(int index) {
checkBoundExclusive(index);
return elementData[index];
}
/**
* Returns an Enumeration of the elements of this Vector. The enumeration
* visits the elements in increasing index order, but is NOT thread-safe.
*
* @return an Enumeration
* @see #iterator()
*/
// No need to synchronize as the Enumeration is not thread-safe!
public Enumeration elements() {
return new Enumeration() {
private int i = 0;
public boolean hasMoreElements() {
return i < elementCount;
}
public Object nextElement() {
if (i >= elementCount)
throw new NoSuchElementException();
return elementData[i++];
}
};
}
/**
* Ensures that <code>minCapacity</code> elements can fit within this
* Vector. If <code>elementData</code> is too small, it is expanded as
* follows: If the <code>elementCount + capacityIncrement</code> is
* adequate, that is the new size. If <code>capacityIncrement</code> is
* non-zero, the candidate size is double the current. If that is not
* enough, the new size is <code>minCapacity</code>.
*
* @param minCapacity
* the desired minimum capacity, negative values ignored
*/
public synchronized void ensureCapacity(int minCapacity) {
if (elementData.length >= minCapacity)
return;
int newCapacity;
if (capacityIncrement <= 0)
newCapacity = elementData.length * 2;
else
newCapacity = elementData.length + capacityIncrement;
// TODO: any way to omit this new?
Object[] newArray = new Object[Math.max(newCapacity, minCapacity)];
System.arraycopy(elementData, 0, newArray, 0, elementCount);
elementData = newArray;
}
/**
* Returns the first element (index 0) in the Vector.
*
* @return the first Object in the Vector
* @throws NoSuchElementException
* the Vector is empty
*/
public synchronized Object firstElement() {
if (elementCount == 0)
throw new NoSuchElementException();
return elementData[0];
}
/**
* Returns the first occurrence of <code>elem</code> in the Vector, or -1
* if <code>elem</code> is not found.
*
* @param elem
* the object to search for
* @return the index of the first occurrence, or -1 if not found
*/
public int indexOf(Object elem) {
return indexOf(elem, 0);
}
/**
* Searches the vector starting at <code>index</code> for object
* <code>elem</code> and returns the index of the first occurrence of this
* Object. If the object is not found, or index is larger than the size of
* the vector, -1 is returned.
*
* @param e
* the Object to search for
* @param index
* start searching at this index
* @return the index of the next occurrence, or -1 if it is not found
* @throws IndexOutOfBoundsException
* if index < 0
*/
public synchronized int indexOf(Object e, int index) {
for (int i = index; i < elementCount; i++)
if (elementData[i].equals(e))
return i;
return -1;
}
/**
* Inserts a new element into the Vector at <code>index</code>. Any
* elements at or greater than index are shifted up one position.
*
* @param obj
* the object to insert
* @param index
* the index at which the object is inserted
* @throws ArrayIndexOutOfBoundsException
* index < 0 || index > size()
* @see #add(int, Object)
*/
public synchronized void insertElementAt(Object obj, int index) {
checkBoundInclusive(index);
if (elementCount == elementData.length)
ensureCapacity(elementCount + 1);
modCount++;
System.arraycopy(elementData, index, elementData, index + 1,
elementCount - index);
elementCount++;
elementData[index] = obj;
}
/**
* Returns true if this Vector is empty, false otherwise
*
* @return true if the Vector is empty, false otherwise
*/
public synchronized boolean isEmpty() {
return elementCount == 0;
}
/**
* Returns the last element in the Vector.
*
* @return the last Object in the Vector
* @throws NoSuchElementException
* the Vector is empty
*/
public synchronized Object lastElement() {
if (elementCount == 0)
throw new NoSuchElementException();
return elementData[elementCount - 1];
}
/**
* Returns the last index of <code>elem</code> within this Vector, or -1
* if the object is not within the Vector.
*
* @param elem
* the object to search for
* @return the last index of the object, or -1 if not found
*/
public int lastIndexOf(Object elem) {
return lastIndexOf(elem, elementCount - 1);
}
/**
* Returns the index of the first occurrence of <code>elem</code>, when
* searching backwards from <code>index</code>. If the object does not
* occur in this Vector, or index is less than 0, -1 is returned.
*
* @param e
* the object to search for
* @param index
* the index to start searching in reverse from
* @return the index of the Object if found, -1 otherwise
* @throws IndexOutOfBoundsException
* if index >= size()
*/
public synchronized int lastIndexOf(Object e, int index) {
checkBoundExclusive(index);
for (int i = index; i >= 0; i--)
if (elementData[i].equals(e))
return i;
return -1;
}
/**
* Removes all elements from the Vector. Note that this does not resize the
* internal data array.
*
* @see #clear()
*/
public synchronized void removeAllElements() {
if (elementCount == 0)
return;
modCount++;
for (int i = 0; i < elementCount; i++) {
elementData[i] = null;
}
elementCount = 0;
}
/**
* Removes the first (the lowestindex) occurance of the given object from
* the Vector. If such a remove was performed (the object was found), true
* is returned. If there was no such object, false is returned.
*
* @param obj
* the object to remove from the Vector
* @return true if the Object was in the Vector, false otherwise
* @see #remove(Object)
*/
public synchronized boolean removeElement(Object obj) {
int idx = indexOf(obj, 0);
if (idx >= 0) {
remove(idx);
return true;
}
return false;
}
/**
* Removes the element at <code>index</code>, and shifts all elements at
* positions greater than index to their index - 1.
*
* @param index
* the index of the element to remove
* @throws ArrayIndexOutOfBoundsException
* index < 0 || index >= size();
* @see #remove(int)
*/
public void removeElementAt(int index) {
remove(index);
}
/**
* Changes the element at <code>index</code> to be <code>obj</code>
*
* @param obj
* the object to store
* @param index
* the position in the Vector to store the object
* @throws ArrayIndexOutOfBoundsException
* the index is out of range
* @see #set(int, Object)
*/
public void setElementAt(Object obj, int index) {
set(index, obj);
}
/**
* Returns the number of elements stored in this Vector.
*
* @return the number of elements in this Vector
*/
public synchronized int size() {
return elementCount;
}
/**
* Explicitly sets the size of the vector (but not necessarily the size of
* the internal data array). If the new size is smaller than the old one,
* old values that don't fit are lost. If the new size is larger than the
* old one, the vector is padded with null entries.
*
* @param newSize
* The new size of the internal array
* @throws ArrayIndexOutOfBoundsException
* if the new size is negative
*/
public synchronized void setSize(int newSize) {
// Don't bother checking for the case where size() == the capacity of
// the
// vector since that is a much less likely case; it's more efficient to
// not do the check and lose a bit of performance in that infrequent
// case
modCount++;
ensureCapacity(newSize);
if (newSize < elementCount)
for (int i = elementCount; i < newSize; i++) {
elementData[i] = null;
}
// Arrays.fill(elementData, newSize, elementCount, null);
elementCount = newSize;
}
/**
* Trims the Vector down to size. If the internal data array is larger than
* the number of Objects its holding, a new array is constructed that
* precisely holds the elements. Otherwise this does nothing.
*/
public synchronized void trimToSize() {
// Don't bother checking for the case where size() == the capacity of
// the
// vector since that is a much less likely case; it's more efficient to
// not do the check and lose a bit of performance in that infrequent
// case
Object[] newArray = new Object[elementCount];
System.arraycopy(elementData, 0, newArray, 0, elementCount);
elementData = newArray;
}
/**
* Removes the element at the specified index, and returns it.
*
* @param index
* the position from which to remove the element
* @return the object removed
* @throws ArrayIndexOutOfBoundsException
* index < 0 || index >= size()
* @since 1.2
*/
public synchronized Object remove(int index) {
checkBoundExclusive(index);
Object temp = elementData[index];
modCount++;
elementCount--;
if (index < elementCount)
System.arraycopy(elementData, index + 1, elementData, index,
elementCount - index);
elementData[elementCount] = null;
return temp;
}
/**
* Puts <code>element</code> into the Vector at position
* <code>index</code> and returns the Object that previously occupied that
* position.
*
* @param index
* the index within the Vector to place the Object
* @param element
* the Object to store in the Vector
* @return the previous object at the specified index
* @throws ArrayIndexOutOfBoundsException
* index < 0 || index >= size()
* @since 1.2
*/
private synchronized Object set(int index, Object element) {
checkBoundExclusive(index);
Object temp = elementData[index];
elementData[index] = element;
return temp;
}
/**
* Compares this to the given object.
*
* @param o
* the object to compare to
* @return true if the two are equal
* @since 1.2
*/
/*
* public synchronized boolean equals(Object o) { // Here just for the
* sychronization. return super.equals(o); }
*/
/**
* Returns a string representation of this Vector in the form "[element0,
* element1, ... elementN]".
*
* @return the String representation of this Vector
*/
public synchronized String toString() {
if (this.size() <= 0)
return "";
StringBuffer sb = new StringBuffer();
sb.append("{\n");
for (int i = 0; i < size(); i++) {
sb.append(elementData[i]);
sb.append(";\n");
}
sb.append("}");
return sb.toString();
}
/**
* Checks that the index is in the range of possible elements (inclusive).
*
* @param index
* the index to check
* @throws ArrayIndexOutOfBoundsException
* if index > size
*/
private void checkBoundInclusive(int index) {
// Implementation note: we do not check for negative ranges here, since
// use of a negative index will cause an ArrayIndexOutOfBoundsException
// with no effort on our part.
if (index > elementCount)
throw new ArrayIndexOutOfBoundsException(index + " > "
+ elementCount);
}
/**
* Checks that the index is in the range of existing elements (exclusive).
*
* @param index
* the index to check
* @throws ArrayIndexOutOfBoundsException
* if index >= size
*/
private void checkBoundExclusive(int index) {
// Implementation note: we do not check for negative ranges here, since
// use of a negative index will cause an ArrayIndexOutOfBoundsException
// with no effort on our part.
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index + " >= "
+ elementCount);
}
}