test&lab

DataLabs/lab5/LinkedQueue.java

@@ -0,0 +1,101 @@
+/**
+   A class that implements the ADT queue by using a chain of nodes
+   that has both head and tail references.
+ 
+   @author Frank M. Carrano
+   @author Timothy M. Henry
+   @version 4.0
+*/
+public final class LinkedQueue<T> implements QueueInterface<T>
+{
+   private Node firstNode; // References node at front of queue
+   private Node lastNode;  // References node at back of queue
+  	
+	public LinkedQueue()
+	{
+		firstNode = null;
+		lastNode = null;
+	} // end default constructor
+
+	public void enqueue(T newEntry)
+	{
+		Node newNode = new Node(newEntry, null);
+
+		if (isEmpty())
+			firstNode = newNode;
+		else
+			lastNode.setNextNode(newNode);
+
+		lastNode = newNode;
+	} // end enqueue
+
+	public T getFront()
+	{
+		if (isEmpty())
+			throw new EmptyQueueException();
+		else
+			return firstNode.getData();
+	} // end getFront
+
+	public T dequeue()
+	{
+		T front = getFront();  // Might throw EmptyQueueException
+		assert firstNode != null;
+		firstNode.setData(null);
+		firstNode = firstNode.getNextNode();
+
+		if (firstNode == null)
+			lastNode = null;
+
+		return front;
+	} // end dequeue
+
+	public boolean isEmpty()
+	{
+		return (firstNode == null) && (lastNode == null);
+	} // end isEmpty
+
+	public void clear()
+	{
+		firstNode = null;
+		lastNode = null;
+	} // end clear
+
+	private class Node
+	{
+		private T    data; // Entry in queue
+		private Node next; // Link to next node
+      
+		private Node(T dataPortion)
+		{
+			data = dataPortion;
+			next = null;
+		} // end constructor
+		
+		private Node(T dataPortion, Node linkPortion)
+		{
+			data = dataPortion;
+			next = linkPortion;
+		} // end constructor
+      
+		private T getData()
+		{
+			return data;
+		} // end getData
+      
+		private void setData(T newData)
+		{
+			data = newData;
+		} // end setData
+      
+		private Node getNextNode()
+		{
+			return next;
+		} // end getNextNode
+		
+		private void setNextNode(Node nextNode)
+		{
+			next = nextNode;
+		} // end setNextNode
+	} // end Node
+} // end LinkedQueue