Help with a java program (prime numbers)

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I'd appreciate help on the task I am given.

A prime number is an integer greater than 1 that is only evenly divisible by 1 and itself.
Complete the isPrime() method, which takes an integer argument. This method
returns a boolean value: true if the argument is prime, and false otherwise. Perform
the required calculations in your method; DO NOT simply use a list of pre-calculated
prime numbers or an if-else chain!

This is what I have.
I don't know where I should place my print statements so that when a number is entered, it tells you whether or not it is prime.

Java

public static boolean isPrime(int n){
System.out.println("Enter a number to determine if it is prime: ");
boolean prime = true;

if (n % 2 == 0){
return false;
}
for (int i = 3; i < n; i++){
if (n % i == 0){
prime = false;
break;
}
return prime
}

Posted 16-May-13 13:39pm

Promethin

Updated 16-May-13 14:09pm

v4

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[no name] 16-May-13 19:43pm

Okay.... and the problem and/or question and/or the help you need is what exactly?

Promethin 16-May-13 20:04pm

Sorry, I posted what I have in the solution area. I don't know where I should place my print statements so that when a number is entered, it tells you whether or not it is prime.

[no name] 16-May-13 20:48pm

How about either before you return from isPrime or right after you call isPrime?

Sergey Alexandrovich Kryukov 16-May-13 19:44pm

Homework? Anyway, you have to solve the problem by yourself, at least show what did you try.
—SA

PIEBALDconsult 16-May-13 21:27pm

That's up to the caller.

Seeing that makes me not want to learn Java.

P.S. Hint -- You don't need to look for factors above the square root.

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_Maxxx_ · Answer 1 · 2013-05-16T19:43:00

YOur

Java

System.out.println("Enter a number to determine if it is prime: ");

shouldn't be inside the function.

OUTSIDE of the function you would need to have (pseudoCode)

Java

Ask the user for a number
Get the number from the user
Call the function, passing the number entered
if (the Function Returned True)
    Tell the user it's a prime
Else
    Tell the user it's not a prime

So the function itself JUST calculates if the number is a prime. That way, if you find a better algorithm in the future (hint see PiebaldConsult's hint!), you can just rewrite that one function without messing up the rest of the program.

Good luck!

Help with a java program (prime numbers)

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