I need to add an invalid entry message when someone enters a wrong value but i can't get it to work. Is there a different way to do it than the way i did? Also my subtraction selection is not working right Here is what I have so far. import java.util.Scanner;

public class ReviewApplication {

public static void main(String[] args) { Scanner keyboard = new Scanner (System.in);

double sum = 0; // Initialize variable

double difference = 0; // Initialize variable

double product = 0;// Initialize variable

double divide = 0;// Initialize variable

double[] array = new double[5];// create array

System.out.print ("Enter 5 floating point numbers: "); // print message

for (int i = 0; i < array.length; i++)// for loop {

array[i] = keyboard.nextDouble (); // get input from user

sum = sum + array[i]; // add array }

char response; // declare variable

while (1 == 1) // while loop

{

System.out.println ("Enter a to add numbers"); // print message System.out.println ("Enter s to subtract"); // print message System.out.println ("Enter m to multiply"); // print message

System.out.println ("Enter d to divide"); // print message System.out.println ("Enter q to exit"); // print message

System.out.print (">>> "); // print message

response = keyboard.next ().charAt (0);// get user input switch (response) // switch case

{

case 'a': // case a

System.out.println ("Sum of Numbers is " + sum);// print message

break; case 's': // switch case

difference = array[0]; // putting array first element in difference

for (int i = 0; i < array.length; i++)// print message { difference = difference - array[i]; }

System.out.println ("the difference is" + difference);// print message

break;

case 'm': // case m

product = array[0]; // putting array first element in product variable

for (int i = 1; i < array.length; i++) // for loop { product = product * array[i]; // multiplying each element } System.out.println ("the product is " + product);// print message

break;

case 'd':

divide = array[0];// putting array first element in divide variable

for (int i = 1; i < array.length; i++)// for loop {

divide = divide / array[i];// dividing each element with its previous one }

System.out.println ("the answer is" + divide); // print message

break;

case 'q': // case q System.exit (0); System.out.println ("bye!"); // print message if (response != 'a' || response != 's' || response != 'm' || response != 'd'|| response != 'q') System.out.println("Invalid menu slection. Try again."); break; } } } }