Class Queue.QImpl 
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Class Queue.QImpl 

java.lang.Object
   |
   +----Queue.QImpl
public class QImpl
extends Object
implements Queue
Class QImpl implements the interface Queue. Operations on the queue interface are synchronized to allow concurrent access.
See Also:
Queue

Variable Index

o head_node
refers to the first element
o num_elem
keep track of queue size
o tail_node
refers to the last element

Constructor Index

o QImpl()
Constructor, creates an empty queue.

Method Index

o clone()
Returns a shallow copy of the queue.
o elements()
Returns an enumeration of the elements in the queue.
o firstElement()
Returns the first element of the queue without removing the element.
o insertFirst(Object)
Insert the specified element into the front of the queue.
o insertLast(Object)
Insert the specified element into the back of the queue.
o lastElement()
Returns the last element of the queue without removing the element.
o removeFirst()
Remove and return an element from the front of the queue.
o removeLast()
Remove and return an element from the back of the queue.
o size()
Returns the number of elements in the queue.

Variables

o num_elem 
  protected int num_elem
keep track of queue size
o head_node 
  protected QNodeImpl head_node
refers to the first element
o tail_node 
  protected QNodeImpl tail_node
refers to the last element

Constructors

o QImpl 
  public QImpl()
Constructor, creates an empty queue.

Methods

o lastElement 
  public synchronized Object lastElement() throws NoSuchElementException
Returns the last element of the queue without removing the element.
Returns:
the last element
o firstElement 
  public synchronized Object firstElement() throws NoSuchElementException
Returns the first element of the queue without removing the element.
Returns:
the first element
o insertFirst 
  public synchronized void insertFirst(Object elem)
Insert the specified element into the front of the queue.
Parameters:
elem - element to be inserted
o insertLast 
  public synchronized void insertLast(Object elem)
Insert the specified element into the back of the queue.
Parameters:
elem - element to be inserted
o removeFirst 
  public synchronized Object removeFirst() throws NoSuchElementException
Remove and return an element from the front of the queue.
Returns:
the element at the front of the queue
Throws: NoSuchElementException
thrown when there are no elements in the queue
o removeLast 
  public synchronized Object removeLast() throws NoSuchElementException
Remove and return an element from the back of the queue.
Returns:
the element at the back of the queue
Throws: NoSuchElementException
thrown when there are no elements in the queue
o size 
  public synchronized int size()
Returns the number of elements in the queue.
o elements 
  public synchronized Enumeration elements()
Returns an enumeration of the elements in the queue.
Returns:
the enumeration
See Also:
Enumeration
o clone 
  public synchronized Object clone()
Returns a shallow copy of the queue.
Overrides:
clone in class Object
See Also:
clone 
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