Java：在方法main中调用方法

Question

FYI: I am a beginner. Also, I understand that calling methods is a novice concept and there are a few threads like this already. My situation is a little different because I am very restricted by pseudo-code that my program must mirror identically. I am having trouble calling methods from other methods, including calling a method from inside main. Here is the pseudo-code followed by the code that I wrote:

PSEUDO-CODE:

// The user enters an integer and the program calculates that many primes
// It uses 3 methods, including the main. All the methods are in the same class
// and should be declared as ‘public static.’

Project Print the First n Primes
    Package printTheFirstNPrimesPackage
        Class PrintTheFirstNPrimes
            Method Main
                Declare numberOfPrimes as integer
Print “How many prime numbers do you want?"
                Read numberOfPrimes from the keyboard
                Call the method: PrintNPrimes(numberOfPrimes)
            end Method (Main)

//          ***********************************************************
//           This method accepts an integer and prints that many prime
//            numbers, starting at 2. 2 is the lowest primt number. 
//          ***********************************************************
            Method void PrintNPrimes(int n)
                declare i as integer
                declare myNum as integer
                myNum = 2   // The first prime number
                i = 0
                loop while i < n    // This could be a ‘for’ loop
                if IsPrime(myNum)   // Call the Isprime method, (see below)
                    i = i + 1
                    print myNum
                End If
                myNum = myNum + 1
                end loop
            end Method PrintNPrimes
//          **********************************************************
//          This method accepts an integer and tests to see if it is 
//            a prime number. If it is prime, the method returns true,
//             otherwise it returns false.
//          **********************************************************
            Method boolean IsPrime(int number)
                Declare result as boolean
                result = true
                declare i as integer
                i = 2
                loop while i < number
                    if ((number % i) == 0)
                        result = false
                        exit loop
                    end if

                end loop
                return result
            end Method

        end Class
    End Package
End Project

JAVA CODE:

package printTheFirstNPrimesPackage;
import java.util.*;

public class PrintTheFirstNPrimes {
    public static void main(String [] args) {
        int numberOfPrimes;
        Scanner primes = new Scanner(System.in);
        System.out.println("How many prime numbers do you want?");
        numberOfPrimes = primes.nextInt();
        // Call the method PrintNPrimes(numberOfPrimes)
    }
    public static void PrintNPrimes(int n) {
        int i;
        int myNum;
        myNum = 2; // The first prime number
        i = 0; {
        while (i < n) 
//      if IsPrime(myNum) // Call the IsPrime method (see below) {
                i = i + 1;
                System.out.println(myNum);
        myNum = myNum + 1;
        }
    }
    public static boolean IsPrime(int number) {
        boolean result;
        result = true;
        int i = 2;
        while (i < number) {
            if ((number % 1) == 0)
                result = false;
            }
        return result;
        }
    }

My main issue is calling the IsPrime method within the if statement. I get an error saying the IsPrime cannot be converted from int to boolean which I knew, but the pseudo-code restricts me from doing much else. I also would like advice on how I should call the PrintNPrimes method within method main. Thanks.

Answer 1

Because your PrintNPrimes is static method, you can just call the method by passing the numberofPrimes .

Example:

 public static void main(String [] args) {
        int numberOfPrimes;
        Scanner primes = new Scanner(System.in);
        System.out.println("How many prime numbers do you want?");
        numberOfPrimes = primes.nextInt();
       PrintNPrimes(numberOfPrimes);
    }
  ..........

Note: Java naming convention suggests that use first letter as small case letter while defining methods.

You can follow same approach to invoke other methods.

Answer 2

if IsPrime(myNum)

needs to be

if (IsPrime(myNum))

Also be sure to restore your curly braces. I don't see any reason why this will cause an error. Please post the exact error message if you still have problems.

Answer 3

Update code below with resolution for both (including if statement) of your compilation errors:

printNPrimes(numberOfPrimes);

if (isPrime(myNum)) // Call the IsPrime method (see below) {

Full updated code:

public static void main(String [] args) {
    int numberOfPrimes;
    Scanner primes = new Scanner(System.in);
    System.out.println("How many prime numbers do you want?");
    numberOfPrimes = primes.nextInt();
    printNPrimes(numberOfPrimes);
}
public static void printNPrimes(int n) {
    int i;
    int myNum;
    myNum = 2; // The first prime number
    i = 0; {
    while (i < n) 
     if (isPrime(myNum)) // Call the IsPrime method (see below) {
            i = i + 1;
            System.out.println(myNum);
    myNum = myNum + 1;
    }
}
public static boolean isPrime(int number) {
    boolean result;
    result = true;
    int i = 2;
    while (i < number) {
        if ((number % 1) == 0)
            result = false;
        }
    return result;
}

I didn't check the logic.