Add Ex 19.2

Author: jsquared21

Exercise_19/Exercise_19_02/Exercise_19_02.class

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+/**********************************************************************************
+* (Implement GenericStack using inheritance) In Listing 19.1, GenericStack is     *
+* implemented using composition. Define a new stack class that extends ArrayList. *
+*                                                                                 *
+* Draw the UML diagram for the classes and then implement GenericStack.           *
+* Write a test program that prompts the user to enter five strings and displays   *
+* them in reverse order.                                                          *
+**********************************************************************************/
+import java.util.Scanner;
+
+public class Exercise_19_02 {
+	/** Main method */
+	public static void main(String[] args) {
+		// Create a Scanner
+		Scanner input = new Scanner(System.in);
+
+		// Create a Stack
+		GenericStack<String> stack = new GenericStack<>(); 
+
+		// Prompt the user to enter five strings
+		System.out.print("Enter five strings: ");
+		for (int i = 0; i < 5; i++) 
+			stack.push(input.next());
+
+		// Display the strings in reverse order
+		while (!stack.isEmpty())
+			System.out.print(stack.pop() + " ");
+		System.out.println();
+	}
+}

Exercise_19/Exercise_19_02/Exercise_19_02.java

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+import java.util.ArrayList;
+
+public class GenericStack<E> extends ArrayList<E> {
+
+	/** Return the element at the top of the stack */
+	public E peek() {
+		return get(size() - 1);
+	}
+
+	/** Push and element on to the stack */
+	public void push(E o) {
+		add(o);
+	}
+
+	/* Return and remove the element 
+	 * on the top of the stack */
+	public E pop() {
+		E o = get(size() - 1);
+		remove(size() - 1);
+		return o;
+	}
+
+	@Override // Override the string method in the ArrayList class
+	public String toString() {
+		return "stack: " + super.toString();
+	}
+}