另一个类JAVA的调用方法

Question

I'm using an external class that contains the method: public static boolean isPrime(int n).

I'm new in java and I don't know how to call a method from another class, I've been reading in other posts and they suggest to create an object, so that's what I did creating TestPrime objeto=new TestPrime(); but the if(objeto.isPrime(arrayInt[i])==true) isn't working.

import com.utad.idcd.redes.PrimeNumber;
public class TestPrime {
    public static void main(String[] args) {
        TestPrime objeto = new TestPrime();
        int arrayInt[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        for (int i = 0; i < 9; i++) {

            System.out.print("El" + arrayInt[i] + "es: ");

            if (objeto.isPrime(arrayInt[i]) == true) {
                System.out.print("primo\n");
            } else {
                System.out.print("no primo\n");
            }
        }    
    } 
}

Answer 1

You have to create object of the PrimeNumber Class

import com.utad.idcd.redes.PrimeNumber;
public class TestPrime {
    public static void main(String[] args) {
        int arrayInt[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        for (int i = 0; i < 9; i++) {

            System.out.print("El" + arrayInt[i] + "es: ");

            if (PrimeNumber.isPrime(arrayInt[i]) == true) {
                System.out.print("primo\n");
            } else {
                System.out.print("no primo\n");
            }
        }    
    } 
}

Now it should run fine.

Edit: sorry, I did not see the method was static; since your method is static and public you can also use static import like:

import static com.utad.idcd.redes.PrimeNumber.isPrime;

and then directly use the function as

if (isPrime(arrayInt[i]) == true) { 

Answer 2

Please look the example below guy,

class PrimeNumber{

public void boolean isPrimeNumber(){

//Your code check the prime number here

}

}

class MainTest {

  public static void main(String[] args) {
    PrimeNumber obj =new PrimeNumber();
    int arrayInt[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    for(int i=0; i<9; i++){

        System.out.print("El" + arrayInt[i] + "es: ");

        if(obj.isPrimeNumber(arrayInt[i])==true){
            System.out.print("primo\n");
        }
        else {
            System.out.print("no primo\n");
        }
   }    
}

}