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why does this work?

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From: dkoleary <dkoleary@olearycomputers.com>

Hi;

New java programmer.  So new, in fact, that I'm still working my way through 
the O'Reilly Head First Java book.  One of the end of chapter questions 
involves identifying if a sample class will compile and what to do to make it 
compile if it won't.

The sample class from chapter 4 is:

class XCopy
{  public static void main(String[] args)
   {  int orig = 42;
      XCopy x = new XCopy();
      int y = x.go(orig);
      System.out.println(orig + " " + y);
   }

   int go(int arg)
   {  return arg * 2;   }
}

The book says that it'll compile and run, displaying "42 84" and, sure enough, 
it does:

$ javac XCopy.java
$ java XCopy
42 84

How come that isn't recursive?  XCopy.main() instantiates a new XCopy. 
Shouldn't that new XCopy instance also instantiate a new XCopy?

I was figuring this would run until the XCopy.go function tried returning a 
number that wouldn't fit in int anymore... That's obviously not the case, but I 
don't know why.

Can someone provide the missing concept?

Thanks.

Doug O'Leary

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Thread

why does this work? "dkoleary" <dkoleary@1:261/38.remove-qhs-this> - 2012-08-08 19:04 +0000
  Re: why does this work? "Daniel Pitts" <daniel.pitts@1:261/38.remove-qhs-this> - 2012-08-08 19:04 +0000
    Re: why does this work? "dkoleary" <dkoleary@1:261/38.remove-k2r-this> - 2012-08-09 18:44 +0000
      Re: why does this work? "Lew" <lew@1:261/38.remove-k2r-this> - 2012-08-09 18:44 +0000
  Re: why does this work? "Eric Sosman" <eric.sosman@1:261/38.remove-r72-this> - 2012-08-08 20:06 +0000
  Re: why does this work? "Roedy Green" <roedy.green@1:261/38.remove-k2r-this> - 2012-08-09 18:44 +0000
    Re: why does this work? "glen herrmannsfeldt" <glen.herrmannsfeldt@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000

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