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Java Was Strongly Influenced by Objective-C

cs.gmu.edu

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Re: Java Was Strongly Influenced by Objective-C

#41

Post by pvg »

blasdel wrote: post #31
pvg wrote: post #15

Earlier quoted context omitted.

There are. Think about classloaders and the whole dynamic code loading thing. Every single object has a class object associated with it.

But can you pass classes around as objects after they're loaded? Do they have a value beyond their identifier?

Yep, you can pass them around, they do have values, in fact, they can have different values for the same type sometimes. This has been the case since well before Java even had reflection - having them around is fairly central to the Java dynamic loading and security model.

Re: Java Was Strongly Influenced by Objective-C

#42

Post by lucifer »

blasdel wrote: post #35
lucifer wrote: post #9

Earlier quoted context omitted.

// unseen? if (foo.getClass() instanceof someClassObject) ...

In this case isn't someClassObject just a literal that's resolved at compile-time and erased into a simple identifier symbol? You can't pass someClassObject as an argument to anything but an operator like new or instanceof , and you can't assign to or from it, it doesn't itself belong to a class. It isn't an object.

> In this case isn't someClassObject just a literal that's resolved at compile-time and erased into a simple identifier symbol?

No. Its a variable assigned in runtime.

   public void yesYouCan (Object foo, Class someClassObject) {
      // compile time?
      if(foo.getClass() instanceof someClassObject) { ... }
   }
Regardless, class and symbolic resolution occur at both compilation (to create the binary clsss files) and in runtime in the JVM (to load and execute the binary generated by the compiler):

http://java.sun.com/docs/books/jls/second_edition/html/execu...

> You can't pass someClassObject as an argument to anything but an operator like new or instanceof, and you can't assign to or from it, it doesn't itself belong to a class. It isn't an object.

No, its quite possible/common to write methods that take class objects as parameters.

Re: Java Was Strongly Influenced by Objective-C

#43

Post by lucifer »

blasdel wrote: post #31
pvg wrote: post #15

Earlier quoted context omitted.

There are. Think about classloaders and the whole dynamic code loading thing. Every single object has a class object associated with it.

But can you pass classes around as objects after they're loaded? Do they have a value beyond their identifier?

When you define a class, say "Foo", instances of Foo are Foo objects. "Foo", itself, is an instance of a class named "Class" which is a direct descendent of the class "Object".

In Java's type system, classes are 'first class objects':

http://en.wikipedia.org/wiki/First-class_object

Re: Java Was Strongly Influenced by Objective-C

#45

Post by allenbrunson »

glhaynes wrote: post #39
bad_user wrote: post #19

Earlier quoted context omitted.

Sure you can ... object.sendMessage(messageName) ;) Or for already built classes ... see java.lang.reflect.Method Personally if I were to choose, I'd trade some syntactic sugar for a decent garbage-collector. But that's just me :)

Objective C 2.0's garbage collector works just fine tyvm

... but not on the iphone, sadly.

Re: Java Was Strongly Influenced by Objective-C

#46

Post by ekiru »

ryanpetrich wrote: post #22
bad_user wrote: post #19

Earlier quoted context omitted.

Sure you can ... object.sendMessage(messageName) ;) Or for already built classes ... see java.lang.reflect.Method Personally if I were to choose, I'd trade some syntactic sugar for a decent garbage-collector. But that's just me :)

Message forwarding is not syntactic sugar!

It is. In Objective C: [obj doFoo] would be analogous to this in a Java-like language: MethodSpec s = new MethodSpec("doFoo"); (obj.hasMethod(ms) ? obj.performMethod(ms) : obj.handleMissingMethod(ms)

However, people associate "syntactic sugar" with a connotation of not being a significant difference. Many very useful tools in programming are merely syntactic sugar. For, while, and similar control flow structures are just syntactic sugar over either continuations or gotos.

Message passing OO is syntactic sugar. As evidence, look at the object system the Gtk folks made for themselves in C, or the various object systems Perl programmers have made for themselves.

The example of object systems in Perl illustrates another point about syntactic sugar: having a language which makes it possible for programmers to add their own syntactic sugar within the language is incredibly powerful. Moose is a great system, and Perl's flexible syntax is what makes it possible(although I don't really know Perl well enough to know how it's implemented, its syntax is very pleasant). CLOS is another example of the power of languages which allow programmers to add their own syntactic sugar.

Syntactic sugar can be very good. Message forwarding not only is a very useful piece of syntactic sugar, but also allows the creation of certain types of very convenient syntactic sugar to a language.

Re: Java Was Strongly Influenced by Objective-C

#47

Post by tedunangst »

pvg wrote: post #26
oopd wrote: post #23

Earlier quoted context omitted.

As pointed out in my post, the alleged influence simply isn't there, or isn't there enough to justify the claim. Someone who cites Smalltalk as their inspiration before going off and creating a statically-typed OO language with primitive types and classes that aren't real objects either didn't understand Smalltalk or deliberately chose to distort the concepts imbued in it enough that they no longer have a right to cl…

They cited Obj-C, not Smalltalk. Specific people and specific aspects of the design are mentioned, you haven't actually described how it isn't influenced by Obj-C. Which, incidentally, has primitive types, the plain C part can do static type-checking, etc. In any event the claim is the design is influenced by Obj-C not that it is actually just like Obj-C, a distinction you seem to have trouble making.

The claim is that interfaces ripped off prototypes. I'd say that interfaces are a lot closer to C++ abstract classes than prototypes. Whatever they claim, here's my test:

Tell a C++ compiler engineer to make language "C++ minus templates and multiple inheritance plus GC" and you'll probably end up very close to Java.

What do you tell an objective-C compiler engineer to get Java? "Start with obc-c and ..."?

Maybe it's convergent independent evolution, but if obc-c is a branch to the left from C and C++ is a branch to the right, then claiming that Java comes from obj-c means Java must have pulled a very hard right early in its development.

Re: Java Was Strongly Influenced by Objective-C

#48

Post by tedunangst »

10ren wrote: post #37
oopd wrote: post #28

Earlier quoted context omitted.

"They cited Obj-C, not Smalltalk." The author also cites Goslings "lots of experience" with Smalltalk. "In any event the claim is the design is influenced by Obj-C not that it is actually just like Obj-C, a distinction you seem to have trouble making." The influence is not sufficient to justify that claim any more than Java's garbage collection would justify its designers in describing Java as "Lispy" or "Lisp-like."

"We were after the C++ programmers. We managed to drag a lot of them about halfway to Lisp." - Guy Steele, co-author of the Java spec

Guy Steele apparently measures distance on a log scale. :)

Re: Java Was Strongly Influenced by Objective-C

#49

Post by martingordon »

inferno0069 wrote: post #6

Perhaps learning Objective-C would make me a better Java coder. Alternately, maybe all the ObjC practices that would translate have already been written up as standard Java patterns or included in the standard Java books and all I'd get from it would be frustration because I can't apply anything neat I see.

One of my favorite things Objective-C has over Java is no NullPointerExceptions (it's legal to send a message to nil).

One of my least favorite things Objective-C has is EXC_BAD_ACCESS (usually caused by memory mismanagement).

Re: Java Was Strongly Influenced by Objective-C

#50

Post by zaphar »

DougBTX wrote: post #13
inferno0069 wrote: post #6

Perhaps learning Objective-C would make me a better Java coder. Alternately, maybe all the ObjC practices that would translate have already been written up as standard Java patterns or included in the standard Java books and all I'd get from it would be frustration because I can't apply anything neat I see.

I'm playing with some Objective-C at the moment. For me the most interesting thing is how blurred the line between ObjC/OOP/message passing and straight C is. It's the first language I've used where you can treat the high level part as not much more than a library with custom syntax. I'm sure the lispers live in this world all the time ;)

Yes we do.
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