Rename year directories to allow natural ordering

year2/semester2/CT2109/Assignments/Assignment-03/code/ArrayStack.java

@@ -0,0 +1,63 @@
+/** Array implementation of Stack ADT  */
+
+import javax.swing.JOptionPane;
+
+public class ArrayStack implements Stack
+{
+   protected int capacity; 			// The actual capacity of the stack array
+   protected static final int CAPACITY = 1000;	// default array capacity
+   protected Object S[];			// array used to implement the stack 
+   protected int top = -1;			// index for the top of the stack
+   
+   public ArrayStack() {
+	   // default constructor: creates stack with default capacity
+	   this(CAPACITY);
+   }
+
+   public ArrayStack(int cap) {
+	  // this constructor allows you to specify capacity of stack
+	  capacity = (cap > 0) ? cap : CAPACITY;
+	  S = new Object[capacity]; 
+   }
+   
+   public void push(Object element) {
+	 if (isFull()) {
+	   JOptionPane.showMessageDialog(null, "ERROR: Stack is full.");
+	   return;
+	 }
+	 top++;
+	 S[top] = element;
+   }
+
+   public Object pop() {
+	  Object element;
+	  if (isEmpty()) {
+	     JOptionPane.showMessageDialog(null, "ERROR: Stack is empty.");
+	     return  null;
+	  }
+	  element = S[top];
+	  S[top] = null;
+	  top--;
+	  return element;
+   }
+
+   public Object top() {
+	 if (isEmpty()) {
+		 JOptionPane.showMessageDialog(null, "ERROR: Stack is empty.");
+		 return null;
+	 }
+	 return S[top];
+   }
+	   
+   public boolean isEmpty() {
+		  return (top < 0);
+   }
+
+   public boolean isFull() {
+		  return (top == capacity-1);
+   }
+
+   public int size() { 
+		 return (top + 1);
+   }
+ }