why the next statement after the while loop doesn't get executed

Question

I am supposed to get the product of the integer entered by user util a number that is less than 1 is entered, and print the product. But when the program does nothing after I enter the numbers. How can I fix this.

Here is the code:

  public static void main(String[] args) {
    Scanner input = new Scanner(System.in); 
    System.out.println("Enter integers: "); 
    int num = 1; 
    int product = 1; 
    while(input.hasNextInt() && num>=0){ 
       num = input.nextInt(); product = product*num; 
     } 
    System.out.print("Product: "+product); 
} 

Answer 1

First, your test num>=0 is not a test for ending the loop when "a number that is less than 1 is entered", since 0 is less then 1 but won't end the loop.

Second, the test of num is done after num has been applied to product . You don't want that.

So you need to test num after getting it, but before applying it to product . If less than 1, you want to end the loop, which you can do with a break statement.

Also, it is generally bad style to put multiple statements on a single line.

System.out.println("Enter integers:");
int product = 1;
while (input.hasNextInt()) {
    int num = input.nextInt();
    if (num < 1)
        break;
    product *= num;
}
System.out.println("Product: " + product);

Answer 2

In your code, the while loop keep running forever. So that's why it do not print anything.

Try this instead:

 while(input.hasNextInt() && num>=0){ 
   num = input.nextInt(); 
   product = product*num; 
   System.out.print("Product: "+product); 
 } 

EDIT: Try to enter the number less than 0 then your while loop should terminate.

Answer 3

You could try something like this:

public static void main(String[] args)
{
    Scanner input = new Scanner(System.in); 
    System.out.println("Enter integers: "); 
    int num = 1; 
    int product = 1;
    while(true)
    {
        try
        {
            num = input.nextInt();
            if(num < 0)
            {
                break;
            }
            product = product * num;
        } catch(InputMismatchException e)
        {
            System.out.println("Please enter a number.");
            input.nextLine();
        }
    }
    System.out.print("Product: "+product);
}