structure
Interface Queue

All Superinterfaces:

Linear, Structure

All Known Implementing Classes:

AbstractQueue, QueueList, QueueArray, QueueVector

public interface Queue

extends Linear

Interface describing a first-in, first-out structure. Values are added at the tail, and removed from the head. Queues are typically used to process values in the order that they appear and to store the state of a buffered object. The structure package provides several implementations of the Queue interface, each of which has its particular strengths and weaknesses.

Example usage:

To compute the sum of the unicode value of every character in the standard input we could use the following:

 public static void main(String[] arguments)
 {
     Queue q = new QueueList();
     int unicodeSum = 0;

     if(arguments.length > 0){
         for(int i=0; i < arguments.length; i++){
	       for(int j=0; j < arguments[i].length(); j++){
		   q.enqueue(new Character(arguments[i].charAt(j)));
	       }
	   }
     }

     while(!q.empty()){
	  char c = ((Character)q.dequeue()).charValue();
	  unicodeSum+=Character.getNumericValue(c);
     }

     System.out.println("Total Value: " + unicodeSum);
 }
 

See Also:

Stack, AbstractQueue, QueueArray, QueueVector, QueueList

Method Summary

void	add(Object value) Add a value to the tail of the queue.
Object	dequeue() Remove a value from the head of the queue.
boolean	empty() Returns true iff the queue is empty.
void	enqueue(Object value) Add a value to the tail of the queue.
Object	get() Fetch the value at the head of the queue.
Object	getFirst() Fetch the value at the head of the queue.
Object	peek() Fetch the value at the head of the queue.
Object	remove() Remove a value form the head of the queue.
int	size() Returns the number of elements in the queue.

Methods inherited from interface structure.Structure

clear, contains, elements, isEmpty, iterator, remove, values

Method Detail

add

public void add(Object value)

Add a value to the tail of the queue.

Specified by:

add in interface Linear

Parameters:

value - The value added.

Postcondition:

the value is added to the tail of the structure

See Also:

enqueue(java.lang.Object)

enqueue

public void enqueue(Object value)

Add a value to the tail of the queue.

Parameters:

value - The value to be added.

Postcondition:

the value is added to the tail of the structure

remove

public Object remove()

Remove a value form the head of the queue.

Specified by:

remove in interface Linear

Precondition:

the queue is not empty

Postcondition:

the head of the queue is removed and returned

Returns:

The value actually removed.

See Also:

dequeue()

dequeue

public Object dequeue()

Remove a value from the head of the queue.

Precondition:

the queue is not empty

Postcondition:

the head of the queue is removed and returned

Returns:

The value removed from the queue.

getFirst

public Object getFirst()

Fetch the value at the head of the queue.

Precondition:

the queue is not empty

Postcondition:

the element at the head of the queue is returned

Returns:

Reference to the first value of the queue.

get

public Object get()

Fetch the value at the head of the queue.

Specified by:

get in interface Linear

Precondition:

the queue is not empty

Postcondition:

the element at the head of the queue is returned

Returns:

Reference to the first value of the queue.

peek

public Object peek()

Fetch the value at the head of the queue.

Precondition:

the queue is not empty

Postcondition:

the element at the head of the queue is returned

Returns:

Reference to the first value of the queue.

empty

public boolean empty()

Returns true iff the queue is empty. Provided for compatibility with java.util.Vector.empty.

Specified by:

empty in interface Linear

Postcondition:

returns true if and only if the queue is empty

Returns:

True iff the queue is empty.

size

public int size()

Returns the number of elements in the queue.

Specified by:

size in interface Linear

Postcondition:

returns the number of elements in the queue

Returns:

number of elements in queue.