package com.mycompany.test;

public class Calculator {

	public static void main(String[] args) {
		int a = 4;
		int b = 2;
		System.out.println(sum(a,b));
		System.out.println(minus(a,b));
	}

	private static int sum(int a, int b) {
		return a + b;
	}
	private static int minus(int a, int b) {
		return a + b;
	}
	
}

package com.mycompany.test;

public class Calculator {

	public static void main(String[] args) {
		int a = 4;
		int b = 2;
		System.out.println(sum(a,b));
		System.out.println(minus(a,b));
	}

	private static int sum(int a, int b) {
		return a + b;
	}
	private static int minus(int a, int b) {
		return a + b;
	}

	private static int mul(int a, int b, Object GPU) {
		int result = 0;
		if( GPU == null ){
			result = a * b;
			return result;
		}
		else{
			result = a * b;
			return result;
		}

	}



}

Add GPU mul function