You can also use Character.getNumericValue(c);

Proof?

Not with modern versions of the java compiler. They now tend to automatically replace string concatenation with a StringBuilder and multiple append(String) calls on it at compile-time.

It also performs unnecessary checking as the details specify a non-zero number will be given.

this solution is wrong. It will add Script to anything divisible by two.

This actually fails the following test case. I assume the marking tests are missing this so that solution passes.

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class CalculatorTest {
    @Test
    public void test2returnsMochaMissing()  {
      assertEquals("mocha_missing!", CaffeineBuzz.caffeineBuzz(2));
    }
}