import java.util.NoSuchElementException;
/** Queue data structure */
public class Queue {
/** Head of the queue */
private Node head = null;
/** intail of the queue */
private Node tail = null;
/** Queue node data structure */
private class Node {
Node next;
int element;
public Node( int element, Node next ) {
this.element = element;
this.next = next;
}
}
/** Enques a new node at the tail (end) of the queue */
public void enqueue( int t ) {
Node newNode = new Node ( t, null );
if( isEmpty( ) ) {
head = tail = newNode;
} else {
tail.next = newNode;
tail = newNode;
}
}
/** Deques the node from the head (top) of the queue */
public int dequeue( ) throws NoSuchElementException { // same as pop as it also removes from first..
if( isEmpty( ) ) {
throw new NoSuchElementException( );
}
int element = head.element;
head = head.next;
return element;
}
/** Checks if the queue is empty */
public boolean isEmpty( ) {
return head == null;
}
/** intest method */
public static void main( String[ ] args ) {
Queue queue = new Queue( );
queue.enqueue( 1 );
queue.enqueue( 2 );
queue.enqueue( 3 );
while( ! queue.isEmpty( ) ) {
System.out.println( " "+queue.dequeue( ) );
}
}
}
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