I. ArrayStackWithIterator

Implement an iterator for the linked implementation of stack. The skeleton of the program is provided for you. You need to give implementation for next()and remove() methods. Please note that this iterator does not support the remove operation so UnsupportedOperationException must be thrown.

Sample Run:

Creating a stack

Creating a stackIterator

Calling stackIterator.next())

Exception caught "Illegal call to next(); iterator is below the bottom of the stack."

Adding to stack Jim, Jess, Jill, Jane, Joe

Accessing the top entry with iterator

hasNext() returned false

Resetting the iterator

The stack contains (from top to bottom):

Joe

Jane

Jill

Jess

Jim

Adding to stack John

peek() returns: John

hasNext() returned false

Resetting the iterator

The stack contains (from top to bottom):

John

Joe

Jane

Jill

Jess

Jim

Calling stackIterator.remove())

Exception caught "remove operation is not supported by this stack iterator."

Done.

Process finished with exit code 0

public final class ArrayStackWithIterator implements StackInterface, Iterable { private T[] stack; // Array of stack entries private int topIndex; // Index of top entry private boolean initialized = false; private static final int DEFAULT_CAPACITY = 50; private static final int MAX_CAPACITY = 10000; public ArrayStackWithIterator() { this(DEFAULT_CAPACITY); } // end default constructor public ArrayStackWithIterator(int initialCapacity) { checkCapacity(initialCapacity); // The cast is safe because the new array contains null entries @SuppressWarnings("unchecked") T[] tempStack = (T[]) new Object[initialCapacity]; this.stack = tempStack; this.topIndex = -1; this.initialized = true; } // end constructor public void push(T newEntry) { checkInitialization(); ensureCapacity(); this.stack[this.topIndex + 1] = newEntry; this.topIndex++; } // end push public T peek() { checkInitialization(); if (isEmpty()) throw new EmptyStackException(); else return this.stack[this.topIndex]; } // end peek public T pop() { checkInitialization(); if (isEmpty()) throw new EmptyStackException(); else { T top = this.stack[this.topIndex]; this.stack[this.topIndex] = null; this.topIndex--; return top; } } // end pop public boolean isEmpty() { return this.topIndex < 0; } // end isEmpty public void clear() { checkInitialization(); // Remove references to the objects in the stack, // but do not deallocate the array while (this.topIndex > -1) { this.stack[this.topIndex] = null; this.topIndex--; } } // end clear // Throws an exception if this object is not initialized. private void checkInitialization() { if (!this.initialized) throw new SecurityException( "ArrayStackWithIterator object is not initialized properly."); } // end checkInitialization // Throws an exception if the client requests a capacity that is too large. private void checkCapacity(int capacity) { if (capacity > MAX_CAPACITY) throw new IllegalStateException("Attempt to create a stack " + "whose capacity exceeds " + "allowed maximum."); } // end checkCapacity // Doubles the size of the array stack if it is full // Precondition: checkInitialization has been called. private void ensureCapacity() { if (this.topIndex >= this.stack.length - 1) // If array is full, double its size { int newLength = 2 * this.stack.length; checkCapacity(newLength); this.stack = Arrays.copyOf(this.stack, newLength); } } // end ensureCapacity public Iterator iterator() { return new StackIterator(); } // end iterator private class StackIterator implements Iterator { private int nextIndex; // Reference to next index in the array private StackIterator() { this.nextIndex = topIndex; } // end default constructor public boolean hasNext() { return nextIndex >= 0; } // end hasNext public T next() { // TODO Project 1   return null; } // end next public void remove() { // TODO Project 1   // throws UnsupportedOperationException } // end remove } // end StackIterator public static void main(String[] args) { System.out.println("Creating a stack"); ArrayStackWithIterator myStack = new ArrayStackWithIterator<>(); System.out.println(" Creating a stackIterator"); Iterator stackIterator = myStack.iterator(); try { System.out.println(" Calling stackIterator.next())"); System.out.println("stackIterator.next() returned = " + stackIterator.next()); } catch (NoSuchElementException nsee) { System.out.println("Exception caught \"" + nsee.getMessage() + "\""); } System.out.println(" Adding to stack Jim, Jess, Jill, Jane, Joe"); myStack.push("Jim"); myStack.push("Jess"); myStack.push("Jill"); myStack.push("Jane"); myStack.push("Joe"); System.out.println(" Accessing the top entry with iterator"); if (stackIterator.hasNext()) { System.out.println("hasNext() returned true"); System.out.println("stackIterator.next() returned " + stackIterator.next()); } else System.out.println("hasNext() returned false"); System.out.println(" Resetting the iterator"); stackIterator = myStack.iterator(); System.out.println("The stack contains (from top to bottom):"); while (stackIterator.hasNext()) System.out.println(stackIterator.next()); System.out.println(" Adding to stack John"); myStack.push("John"); System.out.println("peek() returns: " + myStack.peek()); if (stackIterator.hasNext()) { System.out.println("hasNext() returned true"); System.out.println("stackIterator.next() returned " + stackIterator.next()); } else System.out.println("hasNext() returned false"); System.out.println(" Resetting the iterator"); stackIterator = myStack.iterator(); System.out.println("The stack contains (from top to bottom):"); while (stackIterator.hasNext()) System.out.println(stackIterator.next()); try { System.out.println(" Calling stackIterator.remove())"); stackIterator.remove(); } catch (UnsupportedOperationException uoe) { System.out.println("Exception caught \"" + uoe.getMessage() + "\""); } System.out.println(" Done."); } // end main }