smanek on Hacking a Google Interview - MIT's guide to Google interviews

Comment on Hacking a Google Interview - MIT's guide to Google interviews parent

Yeah, Java doesn't do multimethods (i.e., method dispatch based on runtime argument types).

If Class X has two methods:

  void foo(Object i);
  void foo(Integer i);

then:

  Object test = new Integer(4);
  X x = new X();
  x.foo(test);

will invoke 'void foo(Object o);' based on the compile time type of test.

Java does do dispatch based on the runtime type of X - but it is quite limiting once you are used to having proper multiple dispatch at your disposal.

(caveat: not in front of a javac - this is from memory).

d0mine 17y

You're right. It calls 'void foo(Object o);'

    import junit.framework.TestCase;
    
    public class TestMultimethods extends TestCase {
        public void test() {
          Object test = new Integer(4);                                        
          X x = new X();                                                       
          assertEquals(x.foo(test), "foo(Object)");
        }
    }
    
    class X {
        String foo(Object i) { return "foo(Object)"; }
        String foo(Integer i) { return "foo(Integer)"; }
    }

Comments