java.util
Class Vector

java.lang.Object
  |
  +--java.util.Vector
Direct Known Subclasses:
CloneableVector, ContentProtectedVector, SimpleSortingVector, Stack

public class Vector
extends Object

The 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.

Since:
JDK1.0

Field Summary
protected  int capacityIncrement
          The amount by which the capacity of the vector is automatically incremented when its size becomes greater than its capacity.
protected  int elementCount
          The number of valid components in the vector.
protected  Object[] elementData
          The array buffer into which the components of the vector are stored.
 
Constructor Summary
Vector()
          Constructs an empty vector.
Vector(int initialCapacity)
          Constructs an empty vector with the specified initial capacity.
Vector(int initialCapacity, int capacityIncrement)
          Constructs an empty vector with the specified initial capacity and capacity increment.
 
Method Summary
 void addElement(Object obj)
          Adds the specified component to the end of this vector, increasing its size by one.
 int capacity()
          Returns the current capacity of this vector.
 boolean contains(Object elem)
          Tests if the specified object is a component in this vector.
 void copyInto(Object[] anArray)
          Copies the components of this vector into the specified array.
 Object elementAt(int index)
          Returns the component at the specified index.
 Enumeration elements()
          Returns an enumeration of the components of this vector.
 void ensureCapacity(int minCapacity)
          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.
 Object firstElement()
          Returns the first component of this vector.
 int indexOf(Object elem)
          Searches for the first occurence of the given argument, testing for equality using the equals method.
 int indexOf(Object elem, int index)
          Searches for the first occurence of the given argument, beginning the search at index, and testing for equality using the equals method.
 void insertElementAt(Object obj, int index)
          Inserts the specified object as a component in this vector at the specified index.
 boolean isEmpty()
          Tests if this vector has no components.
 Object lastElement()
          Returns the last component of the vector.
 int lastIndexOf(Object elem)
          Returns the index of the last occurrence of the specified object in this vector.
 int lastIndexOf(Object elem, int index)
          Searches backwards for the specified object, starting from the specified index, and returns an index to it.
 void removeAllElements()
          Removes all components from this vector and sets its size to zero.
 boolean removeElement(Object obj)
          Removes the first occurrence of the argument from this vector.
 void removeElementAt(int index)
          Deletes the component at the specified index.
 void setElementAt(Object obj, int index)
          Sets the component at the specified index of this vector to be the specified object.
 void setSize(int newSize)
          Sets the size of this vector.
 int size()
          Returns the number of components in this vector.
 String toString()
          Returns a string representation of this vector.
 void trimToSize()
          Trims the capacity of this vector to be the vector's current size.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

capacityIncrement

protected int capacityIncrement
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 0, the capacity of the vector is doubled each time it needs to grow.
Since:
JDK1.0

elementCount

protected int elementCount
The number of valid components in the vector.
Since:
JDK1.0

elementData

protected Object[] elementData
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
Constructor Detail

Vector

public Vector()
Constructs an empty vector.
Since:
JDK1.0

Vector

public Vector(int initialCapacity)
Constructs an empty vector with the specified initial capacity.
Parameters:
initialCapacity - the initial capacity of the vector.
Since:
JDK1.0

Vector

public Vector(int initialCapacity,
              int capacityIncrement)
Constructs an empty vector with the specified initial capacity and capacity increment.
Parameters:
initialCapacity - the initial capacity of the vector.
capacityIncrement - the amount by which the capacity is increased when the vector overflows.
Throws:
IllegalArgumentException - if the specified initial capacity is negative
Method Detail

addElement

public void addElement(Object obj)
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.
Parameters:
obj - the component to be added.
Since:
JDK1.0

capacity

public int capacity()
Returns the current capacity of this vector.
Returns:
the current capacity of this vector.
Since:
JDK1.0

contains

public boolean contains(Object elem)
Tests if the specified object is a component in this vector.
Parameters:
elem - an object.
Returns:
true if the specified object is a component in this vector; false otherwise.
Since:
JDK1.0

copyInto

public void copyInto(Object[] anArray)
Copies the components of this vector into the specified array. The array must be big enough to hold all the objects in this vector.
Parameters:
anArray - the array into which the components get copied.
Since:
JDK1.0

elementAt

public Object elementAt(int index)
Returns the component at the specified index.
Parameters:
index - an index into this vector.
Returns:
the component at the specified index.
Throws:
ArrayIndexOutOfBoundsException - if an invalid index was given.
Since:
JDK1.0

elements

public Enumeration elements()
Returns an enumeration of the components of this vector.
Returns:
an enumeration of the components of this vector.
Since:
JDK1.0
See Also:
Enumeration

ensureCapacity

public void ensureCapacity(int minCapacity)
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.
Parameters:
minCapacity - the desired minimum capacity.
Since:
JDK1.0

firstElement

public Object firstElement()
Returns the first component of this vector.
Returns:
the first component of this vector.
Throws:
NoSuchElementException - if this vector has no components.
Since:
JDK1.0

indexOf

public int indexOf(Object elem)
Searches for the first occurence of the given argument, testing for equality using the equals method.
Parameters:
elem - an object.
Returns:
the index of the first occurrence of the argument in this vector; returns -1 if the object is not found.
Since:
JDK1.0
See Also:
Object.equals(java.lang.Object)

indexOf

public int indexOf(Object elem,
                   int index)
Searches for the first occurence of the given argument, beginning the search at index, and testing for equality using the equals method.
Parameters:
elem - an object.
index - the index to start searching from.
Returns:
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.
Since:
JDK1.0
See Also:
Object.equals(java.lang.Object)

insertElementAt

public void insertElementAt(Object obj,
                            int index)
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.

Parameters:
obj - the component to insert.
index - where to insert the new component.
Throws:
ArrayIndexOutOfBoundsException - if the index was invalid.
Since:
JDK1.0
See Also:
size()

isEmpty

public boolean isEmpty()
Tests if this vector has no components.
Returns:
true if this vector has no components; false otherwise.
Since:
JDK1.0

lastElement

public Object lastElement()
Returns the last component of the vector.
Returns:
the last component of the vector, i.e., the component at index size() - 1.
Throws:
NoSuchElementException - if this vector is empty.
Since:
JDK1.0

lastIndexOf

public int lastIndexOf(Object elem)
Returns the index of the last occurrence of the specified object in this vector.
Parameters:
elem - the desired component.
Returns:
the index of the last occurrence of the specified object in this vector; returns -1 if the object is not found.
Since:
JDK1.0

lastIndexOf

public int lastIndexOf(Object elem,
                       int index)
Searches backwards for the specified object, starting from the specified index, and returns an index to it.
Parameters:
elem - the desired component.
index - the index to start searching from.
Returns:
the index of the last occurrence of the specified object in this vector at position index or earlier in the vector; -1 if the object is not found.
Since:
JDK1.0

removeAllElements

public void removeAllElements()
Removes all components from this vector and sets its size to zero.
Since:
JDK1.0

removeElement

public boolean removeElement(Object 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.
Parameters:
obj - the component to be removed.
Returns:
true if the argument was a component of this vector; false otherwise.
Since:
JDK1.0

removeElementAt

public void removeElementAt(int index)
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.

Parameters:
index - the index of the object to remove.
Throws:
ArrayIndexOutOfBoundsException - if the index was invalid.
Since:
JDK1.0
See Also:
size()

setElementAt

public void setElementAt(Object obj,
                         int index)
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.

Parameters:
obj - what the component is to be set to.
index - the specified index.
Throws:
ArrayIndexOutOfBoundsException - if the index was invalid.
Since:
JDK1.0
See Also:
size()

setSize

public void setSize(int newSize)
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.
Parameters:
newSize - the new size of this vector.
Since:
JDK1.0

size

public int size()
Returns the number of components in this vector.
Returns:
the number of components in this vector.
Since:
JDK1.0

toString

public String toString()
Returns a string representation of this vector.
Overrides:
toString in class Object
Returns:
a string representation of this vector.
Since:
JDK1.0

trimToSize

public void trimToSize()
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



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