operator.py

from py4j.java_gateway import JavaGateway

class Addition(object):
    def doOperation(self, i, j):
        return i + j

    class Java:
        implements = ['OperatorExample$Operator']

if __name__ == '__main__':
    gateway = JavaGateway(start_callback_server=True)
    operator = Addition()
    numbers = gateway.entry_point.randomBinaryOperator(operator)
    print(numbers)
    gateway.shutdown()

OperatorExample.java

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import py4j.GatewayServer;

public class OperatorExample {

    // To prevent integer overflow
    private final static int MAX = 1000;

    public interface Operator {

        public int doOperation(int i, int j);

    }

    public List<Integer> randomBinaryOperator(Operator op) {
        Random random = new Random();
        List<Integer> numbers = new ArrayList<Integer>();
        numbers.add(random.nextInt(MAX));
        numbers.add(random.nextInt(MAX));
        numbers.add(op.doOperation(numbers.get(0), numbers.get(1)));
        return numbers;
    }

    public static void main(String[] args) {
        GatewayServer server = new GatewayServer(new OperatorExample());
        server.start();
    }

}