Java Foundations

Write a class ArrayStack that implements the StackADT interface using arrays, and also defines a toString method to print out the contents of the stack.

Hint: it is helpful to write a main() method in the ArrayStack class that does a quick test to be sure it works correctly. Do some very brief testing such as creating an object, pushing a few items, printing the stack, popping the items, printing them on their way out, etc.

2. Write a class called ArrayPalindrome. ArrayPalindrome is to have the following in stance variables and methods:

(a) Three ArrayStack instance variables.

(b) The constructor will take no parameters and will create the three stacks of type ArrayStack.

(c) A public method called isPalindrome that takes a string parameter and returns a boolean. The incoming string will be checked to see if it's a palindrome. You will need to examine the characters of the string one at a time and push them onto one of the stacks. The charAt(index) method will be helpful here. Recall also the Character char wrapper class. Be sure to look at the String API for other useful methods.

3. Write a main method in ArrayPalindrome that tests several strings, both palindromes and non-palindromes. Be sure to test any boundary conditions. This is what we will evaluate to test the completeness of your lab. Do not ask for input from the user, instead select a set of test strings. Print out the string, and then "is a palindrome" or "is not a Palindrome". Test at least 5 strings.

Hint: you may want to write a clear method that removes all elements from the three stacks so you can reuse the same ArrayPalindrome object.

StackADT.java

/** * Defines the interface to a stack collection. * * @author Java Foundations * @version 4.0 */ public interface StackADT { /** * Adds the specified element to the top of this stack. * * @param element element to be pushed onto the stack */ public void push(T element);

/** * Removes and returns the top element from this stack. * * @return the element removed from the stack * @throws EmptyCollectionException if the stack is empty */ public T pop();

/** * Returns the top element of this stack without removing it from the stack. * * @return the element on top of the stack. It is not removed from the stack * @throws EmptyCollectionException if the stack is empty */ public T peek();

/** * Returns true if this stack contains no elements. * * @return true if the stack is empty, false if the stack is not empty */ public boolean isEmpty();

/** * Returns the number of elements in this stack. * * @return the number of elements in the stack */ public int size();

}

EmptyCollectionException.java

/** * Represents the situation in which a collection is empty. * * @author Java Foundations * @version 4.0 */ public class EmptyCollectionException extends RuntimeException { /** * Sets up this exception with an appropriate message. * @param collection the name of the collection */ public EmptyCollectionException(String collection) { super("The " + collection + " is empty."); } } ArrayStack.java

import java.util.Arrays;

public class ArrayStack implements StackADT { // data fields private T[] stack; // holds the elements private int top; // size and index above top elt private static final int DEFAULT_CAPACITY = 100; // constructor public ArrayStack() { this(DEFAULT_CAPACITY); } public ArrayStack(int initialCapacity) { this.top = 0; this.stack = (T[])(new Object[initialCapacity]); } @Override public void push(T element) { // check for full.stack. if full, expand if(this.size() == this.stack.length) { this.expandStackArray(); } // put elt in stack this.stack[top] = element; this.top++; } /** * Double the size of the data field array named stack and copy over all handles */ private void expandStackArray() { this.stack = Arrays.copyOf(this.stack, this.stack.length * 2); } @Override public T pop() { T topElt = this.peek(); this.top--; this.stack[top] = null; return topElt; } @Override public T peek() { // check for empty stack if(this.isEmpty()) { throw new EmptyCollectionException("ArrayStack"); } // once we know stack is empty, get the top element return this.stack[top-1]; } @Override public boolean isEmpty() { return (this.top == 0); } @Override public int size() { return this.top; } @Override public String toString() { String s = ""; s = s + "Stack of size " + this.size() + " containing (top on the right): "; for(int i = 0; i < this.top; i++) { s = s + this.stack[i] + ", "; } return s; } // tester for ArrayStack public static void main(String [] args) { ArrayStack s = new ArrayStack(3); s.push("hi"); s.push("bye"); s.push("blahblah"); s.push("EXPANDED!"); System.out.println(s); System.out.println("Pop n' Print:"); while(s.isEmpty() == false) { System.out.println(s.pop()); } } }

ArrayPallindrone.java

public class ArrayPallindrome { private ArrayStack first; private ArrayStack second; private ArrayStack reversed; // constructor public ArrayPalindrome() { this.first = new ArrayStack(); this.second = new ArrayStack(); this.reversed = new ArrayStack(); }

public static void main(String[] args) { ArrayPalindrome pal = new ArrayPalindrome(); if(pal.isPalindrome("bob")) { System.out.println("bob is a palindrome"); } else { System.out.println("bob is not a palidrone"); } // TODO Auto-generated method stub

} /** * Test the input string * @param input string to be tested for palindromity * @return true if input is palindrome */ public boolean isPalindrome(String input)

}