Vector class implements a growable array of
* objects. Like an array, it contains components that can be
* accessed using an integer index. However, the size of a
* Vector can grow or shrink as needed to accommodate
* adding and removing items after the Vector has been created.
*
* Each vector tries to optimize storage management by maintaining a
* capacity and a capacityIncrement. The
* 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
* capacityIncrement. An application can increase the
* capacity of a vector before inserting a large number of
* components; this reduces the amount of incremental reallocation.
*
* @author Lee Boynton
* @author Jonathan Payne
* @version 1.36, 01/28/97
* @since JDK1.0
*/
public
class Vector implements Cloneable, java.io.Serializable {
/**
* The array buffer into which the components of the vector are
* stored. The capacity of the vector is the length of this array buffer.
*
* @since JDK1.0
*/
protected Object elementData[];
/**
* The number of valid components in the vector.
*
* @since JDK1.0
*/
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 is 0, the capacity of the vector is
* doubled each time it needs to grow.
*
* @since JDK1.0
*/
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.
* @since JDK1.0
*/
public Vector(int initialCapacity, int capacityIncrement) {
super();
this.elementData = new Object[initialCapacity];
this.capacityIncrement = capacityIncrement;
}
/**
* Constructs an empty vector with the specified initial capacity.
*
* @param initialCapacity the initial capacity of the vector.
* @since JDK1.0
*/
public Vector(int initialCapacity) {
this(initialCapacity, 0);
}
/**
* Constructs an empty vector.
*
* @since JDK1.0
*/
public Vector() {
this(10);
}
/**
* Copies the components of this vector into the specified array.
* The array must be big enough to hold all the objects in this vector.
*
* @param anArray the array into which the components get copied.
* @since JDK1.0
*/
public final synchronized void copyInto(Object anArray[]) {
int i = elementCount;
while (i-- > 0) {
anArray[i] = elementData[i];
}
}
/**
* Trims the capacity of this vector to be the vector's current
* size. An application can use this operation to minimize the
* storage of a vector.
*
* @since JDK1.0
*/
public final synchronized void trimToSize() {
int oldCapacity = elementData.length;
if (elementCount < oldCapacity) {
Object oldData[] = elementData;
elementData = new Object[elementCount];
System.arraycopy(oldData, 0, elementData, 0, 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.
*
* @param minCapacity the desired minimum capacity.
* @since JDK1.0
*/
public final synchronized void ensureCapacity(int minCapacity) {
int oldCapacity = elementData.length;
if (minCapacity > oldCapacity) {
Object oldData[] = elementData;
int newCapacity = (capacityIncrement > 0) ?
(oldCapacity + capacityIncrement) : (oldCapacity * 2);
if (newCapacity < minCapacity) {
newCapacity = minCapacity;
}
elementData = new Object[newCapacity];
System.arraycopy(oldData, 0, elementData, 0, elementCount);
}
}
/**
* Sets the size of this vector. If the new size is greater than the
* current size, new null items are added to the end of
* the vector. If the new size is less than the current size, all
* components at index newSize and greater are discarded.
*
* @param newSize the new size of this vector.
* @since JDK1.0
*/
public final synchronized void setSize(int newSize) {
if (newSize > elementCount) {
ensureCapacity(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 of this vector.
* @since JDK1.0
*/
public final int capacity() {
return elementData.length;
}
/**
* Returns the number of components in this vector.
*
* @return the number of components in this vector.
* @since JDK1.0
*/
public final int size() {
return elementCount;
}
/**
* Tests if this vector has no components.
*
* @return true if this vector has no components;
* false otherwise.
* @since JDK1.0
*/
public final boolean isEmpty() {
return elementCount == 0;
}
/**
* Returns an enumeration of the components of this vector.
*
* @return an enumeration of the components of this vector.
* @see java.util.Enumeration
* @since JDK1.0
*/
public final synchronized Enumeration elements() {
return new VectorEnumerator(this);
}
/**
* Tests if the specified object is a component in this vector.
*
* @param elem an object.
* @return true if the specified object is a component in
* this vector; false otherwise.
* @since JDK1.0
*/
public final boolean contains(Object elem) {
return indexOf(elem, 0) >= 0;
}
/**
* Searches for the first occurence of the given argument, testing
* for equality using the equals method.
*
* @param elem an object.
* @return the index of the first occurrence of the argument in this
* vector; returns -1 if the object is not found.
* @see java.lang.Object#equals(java.lang.Object)
* @since JDK1.0
*/
public final int indexOf(Object elem) {
return indexOf(elem, 0);
}
/**
* Searches for the first occurence of the given argument, beginning
* the search at index, and testing for equality using
* the equals method.
*
* @param elem an object.
* @param index the index to start searching from.
* @return the index of the first occurrence of the object argument in
* this vector at position index or later in the
* vector; returns -1 if the object is not found.
* @see java.lang.Object#equals(java.lang.Object)
* @since JDK1.0
*/
public final synchronized int indexOf(Object elem, int index) {
for (int i = index ; i < elementCount ; i++) {
if (elem.equals(elementData[i])) {
return i;
}
}
return -1;
}
/**
* Returns the index of the last occurrence of the specified object in
* this vector.
*
* @param elem the desired component.
* @return the index of the last occurrence of the specified object in
* this vector; returns -1 if the object is not found.
* @since JDK1.0
*/
public final int lastIndexOf(Object elem) {
return lastIndexOf(elem, elementCount-1);
}
/**
* Searches backwards for the specified object, starting from the
* specified index, and returns an index to it.
*
* @param elem the desired component.
* @param index the index to start searching from.
* @return the index of the last occurrence of the specified object in this
* vector at position less than index in the vector;
* -1 if the object is not found.
* @since JDK1.0
*/
public final synchronized int lastIndexOf(Object elem, int index) {
for (int i = index ; i >= 0 ; i--) {
if (elem.equals(elementData[i])) {
return i;
}
}
return -1;
}
/**
* Returns the component at the specified index.
*
* @param index an index into this vector.
* @return the component at the specified index.
* @exception ArrayIndexOutOfBoundsException if an invalid index was
* given.
* @since JDK1.0
*/
public final synchronized Object elementAt(int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
}
/* Since try/catch is free, except when the exception is thrown,
put in this extra try/catch to catch negative indexes and
display a more informative error message. This might not
be appropriate, especially if we have a decent debugging
environment - JP. */
try {
return elementData[index];
} catch (ArrayIndexOutOfBoundsException e) {
throw new ArrayIndexOutOfBoundsException(index + " < 0");
}
}
/**
* Returns the first component of this vector.
*
* @return the first component of this vector.
* @exception NoSuchElementException if this vector has no components.
* @since JDK1.0
*/
public final synchronized Object 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
* size() - 1.
* @exception NoSuchElementException if this vector is empty.
* @since JDK1.0
*/
public final synchronized Object lastElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData[elementCount - 1];
}
/**
* Sets the component at the specified index of this
* vector to be the specified object. The previous component at that
* position is discarded.
*
* The index must be a value greater than or equal to 0
* and less than the current size of the vector.
*
* @param obj what the component is to be set to.
* @param index the specified index.
* @exception ArrayIndexOutOfBoundsException if the index was invalid.
* @see java.util.Vector#size()
* @since JDK1.0
*/
public final synchronized void setElementAt(Object 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
* index is shifted downward to have an index one
* smaller than the value it had previously.
*
* The index must be a value greater than or equal to 0
* and less than the current size of the vector.
*
* @param index the index of the object to remove.
* @exception ArrayIndexOutOfBoundsException if the index was invalid.
* @see java.util.Vector#size()
* @since JDK1.0
*/
public final synchronized void removeElementAt(int index) {
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 index. Each component in this vector with
* an index greater or equal to the specified 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 0
* and less than or equal to the current size of the vector.
*
* @param obj the component to insert.
* @param index where to insert the new component.
* @exception ArrayIndexOutOfBoundsException if the index was invalid.
* @see java.util.Vector#size()
* @since JDK1.0
*/
public final synchronized void insertElementAt(Object obj, int index) {
if (index >= elementCount + 1) {
throw new ArrayIndexOutOfBoundsException(index
+ " > " + elementCount);
}
ensureCapacity(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.
*
* @param obj the component to be added.
* @since JDK1.0
*/
public final synchronized void addElement(Object obj) {
ensureCapacity(elementCount + 1);
elementData[elementCount++] = obj;
}
/**
* Removes the first 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.
*
* @param obj the component to be removed.
* @return true if the argument was a component of this
* vector; false otherwise.
* @since JDK1.0
*/
public final synchronized boolean removeElement(Object obj) {
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.
*
* @since JDK1.0
*/
public final synchronized void removeAllElements() {
for (int i = 0; i < elementCount; i++) {
elementData[i] = null;
}
elementCount = 0;
}
/**
* Returns a clone of this vector.
*
* @return a clone of this vector.
* @since JDK1.0
*/
public synchronized Object clone() {
try {
Vector v = (Vector)super.clone();
v.elementData = new Object[elementCount];
System.arraycopy(elementData, 0, v.elementData, 0, elementCount);
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
/**
* Returns a string representation of this vector.
*
* @return a string representation of this vector.
* @since JDK1.0
*/
public final synchronized String toString() {
int max = size() - 1;
StringBuffer buf = new StringBuffer();
Enumeration e = elements();
buf.append("[");
for (int i = 0 ; i <= max ; i++) {
String s = e.nextElement().toString();
buf.append(s);
if (i < max) {
buf.append(", ");
}
}
buf.append("]");
return buf.toString();
}
}
final
class VectorEnumerator implements Enumeration {
Vector vector;
int count;
VectorEnumerator(Vector v) {
vector = v;
count = 0;
}
public boolean hasMoreElements() {
return count < vector.elementCount;
}
public Object nextElement() {
synchronized (vector) {
if (count < vector.elementCount) {
return vector.elementData[count++];
}
}
throw new NoSuchElementException("VectorEnumerator");
}
}