Prime Number Determination [final check!]

[UNDER-18 FG]

Hi, I had to make a java coding that will determine if a number is a prime number or not. Here's the coding I did:

    import.java.util.Scanner;
     public class PrimeNumber
    {
    public static void main(String args[]) 
     {
    int n;
    Scanner Prime = new Scanner(System.in);
    System.out.println(" Please enter a number: ");
    n = Prime.nextInt();
    System.out.println(isPrime(n));
    }
    static boolean isPrime(int n) {
    if (n%2==0) return false;
    for(int i=3;i*i<=n;i+=2) {
    if(n%i==0)
    return false;
    }
    return true;
    }
    } 

And I got just 1 more error to correct here:

PrimeNumber.java:1: error: <identifier> expected
    import.java.util.Scanner;
          ^
1 error

Can anyone please shed some light on correcting this 1 error in my java coding here? Thanks in advance!

[JamesCherrill]

Look up the correct syntax for the import statement - you have an extra . that shoudn't be there.

[UNDER-18 FG]

Alright. I did the correction. And now the coding has no more errrors. And here's the coding:

    import java.util.Scanner;
    public class PrimeNumber
    {
    public static void main(String args[])
    {
    int n;
    Scanner Prime = new Scanner(System.in);
    System.out.println(" Please enter a number: ");
    n = Prime.nextInt();
    System.out.println(isPrime(n));
    }
    static boolean isPrime(int n) {
    if (n%2==0)return false;

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

And here's the output when I gave an input number of 3:

Please enter a number: 
3
true

BUT THE PROBLEM HERE IS that I want the output to return **" This is a prime number " **if the input number given is a prime number

AND

I want the output to return " This is NOT a prime number " if the input number given is NOT a prime number.

So, can anyone please help me to improvise this coding to produce the output I want?
Thanks in advance!

[Lucaci Andrew]

Here, this should do it. I just replaced the

System.out.println(isPrime(n));

part, which would print true or false, with an if

if (isPrime(n))
    System.out.println("The number is prime.\n");
else 
    System.out.println("The number is not prime.\n");

Here's the code:

import java.util.Scanner;
public class PrimeNumber{
    public static void main(String args[]){
        int n;
        Scanner Prime = new Scanner(System.in);
        System.out.println(" Please enter a number: ");
        n = Prime.nextInt();
        if (isPrime(n))
            System.out.println("The number is prime.\n");
        else 
            System.out.println("The number is not prime.\n");
    }

    static boolean isPrime(int n) {
        if (n%2==0)return false;
        for(int i=3;i*i<=n;i+=2) {
            if(n%i==0)
                return false;
        }
        return true;
    }
} 

This is a trivial task. You should probably read your coursebook/tutorials, I bet you'll find the answers there.

[UNDER-18 FG]

Thanks, Lucaci Andrew. Can you also leave a comment for each lines of the coding in explainations of what each line's purpose is for? Like this one I did here(but it's not complete since I do not know all the main functions and purposes of each lines in this coding..)

    import java.util.Scanner;
    public class PrimeNumber{ //The class name here is PrimeNumber
    public static void main(String args[]){
    int n;
    Scanner Prime = new Scanner(System.in);
    System.out.println(" Please enter a number: ");
    n = Prime.nextInt();
    if (isPrime(n))
    System.out.println("The number is prime.\n");
    else
    System.out.println("The number is not prime.\n");
    }
    static boolean isPrime(int n) {
    if (n%2==0)return false;
    for(int i=3;i*i<=n;i+=2) { //This line defines an integer 'i' as the integer other than 1 and the given number. That means, i>2 and i<num.
    if(n%i==0)
    return false;
    }
    return true;
    }

Hope you can lend some advisable solutions on this, thanks in advance!

[Lucaci Andrew]

Well it's your function, so you know what you did in there. I just added that if statement. Also, as I told you before, this things are quite elementary, and you'll find them in any programming book. I suggest you to review your course/lecture and re-read it, or read your course book.