Java
UNIT CHALLENGES

CHALLENGE

CHALLENGE 3 – PRIME TIME

Write a program that asks the user for a number and outputs whether or not it is a prime number.

HINTS

· Recall that a prime number is a number that is only divisible by itself and by 1.

· We can check if number n is divisible by number d by using:

if (n % d == 0)

· For n to be prime, we need to check all numbers between 1 and n to see if they can divide n. So, we need to loop from 2 to n-1 (or from n-1 down to 2).

PSEUDOCODE

Here is a possible pseudocode to create your program.

Get number n from user.
Set variable factorsFound to zero.

Loop so d takes on all numbers from 2 to n-1
{
if n can be divided by d
{
Increment factorsFound by 1
}
}

If factorFound is zero
{
Output: It's a prime number!
}
Else
{
Output: It's not a prime number!
}