assignment

assignments/AssigmentS5/LinkedStack.java

@@ -0,0 +1,110 @@
+//Note: We are using the class LinkedStack instead of 
+//      the class OurStack that the book uses.
+/**
+   A class that checks whether the parentheses, brackets, and braces 
+   in a string occur in left/right pairs.
+   @author Frank M. Carrano, Timothy M. Henry
+   @version 5.0 */
+public class LinkedStack<T> implements StackInterface<T>
+{
+    private Node firstNode;       // Reference to first node
+    private int numberOfEntries;
+
+    public LinkedStack()
+    {
+        firstNode = null;
+        numberOfEntries = 0;
+    } // end default constructor
+    
+    /** Adds a new entry to the top of this stack.
+        @param newEntry  An object to be added to the stack. */
+    public void push(T newEntry)
+    {
+        // Add to beginning of chain:
+        Node newNode = new Node(newEntry);
+        newNode.setNextNode(firstNode);  // Make new node reference rest of chain
+                         // (firstNode is null if chain is empty)
+        firstNode = newNode;       // New node is at beginning of chain
+        numberOfEntries++;       
+    }
+
+    /** Removes and returns this stack's top entry.
+        @return  The object at the top of the stack. 
+        @throws  EmptyStackException if the stack is empty before the operation. */
+    public T pop()
+    {
+        T result = null;
+        if (firstNode != null)
+        {
+            Node removingNode = firstNode;
+            result = removingNode.getData();
+            firstNode = firstNode.getNextNode();
+            numberOfEntries--;
+        }
+        return result;        
+    }
+  
+    /** Retrieves this stack's top entry.
+        @return  The object at the top of the stack.
+        @throws  EmptyStackException if the stack is empty. */
+    public T peek()
+    {
+        T result = null;
+        if (firstNode != null)
+            result = firstNode.getData();
+        return result;
+    }
+
+    /** Detects whether this stack is empty.
+        @return  True if the stack is empty. */
+    public boolean isEmpty()
+    {
+         return numberOfEntries == 0;
+    }
+  
+    /** Removes all entries from this stack. */
+    public void clear()
+    {
+        firstNode = null;
+    }  
+
+    // @author Frank M. Carrano, Timothy M. Henry
+    // @version 5.0 */
+    private class Node
+    {
+        private T    data;  // Entry in bag
+        private Node next;  // Link to next node
+
+        private Node(T dataPortion)
+        {
+            this(dataPortion, null);
+        } // end constructor
+
+        private Node(T dataPortion, Node nextNode)
+        {
+            data = dataPortion;
+            next = nextNode;
+        } // 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 LinkedStack