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.
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.
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.
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.
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