Why, after compiling an interface, "default" method modifier is gone from "javap -v"?

Question

I have observed, that after compiling an interface containing default method definition, like:

interface Delta {

    default void someMethod() {
        System.out.println("Hi.");
    }

}

and after disassembling the respective .class file (including only corresponding snippet here):

javap -v Delta.class

####

{
  public void someMethod();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     #1                  // Field java/lang/System.out:Ljava/io/PrintStream;
         3: ldc           #2                  // String Hi.
         5: invokevirtual #3                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
         8: return
      LineNumberTable:
        line 10: 0
        line 11: 8
}

default modifier is gone.

Could anyone explain - why?

I am running:

openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)

_{Note, that I am aware, that all methods are implicitly public, when no modifier is defined. So, I am not asking why public modifier is present in the compiled version of the file.}

what java version, obviously. might be a bug in `javap` - since I am on jdk-16 and I do see it. — Eugene, Jul 30 '21 at 19:30
@Eugene good point. It's `openjdk version "11.0.2" 2019-01-15`. — Giorgi Tsiklauri, Jul 30 '21 at 19:31
The question is really why `javap` doesn't show the `default` modifier. The modifier itself is source code, not bytecode, so it wouldn't be literally present in the compiled bytecode (and the fact that the method isn't marked as `abstract` is enough to know it has a default implementation). — kaya3, Jul 30 '21 at 19:32
@kaya3 then why all other modifiers are present in the disassembled one? I would really appreciate if you could just try to help me understand my point, without just rushing into demonstrating *how wrong my question is*. — Giorgi Tsiklauri, Jul 30 '21 at 19:33
eh, sorry, don't have the same exact version, but on a higher 11 (`11.0.9.1`), I see it. On Mac, btw. — Eugene, Jul 30 '21 at 19:33
@GiorgiTsiklauri I did read your question, and I'm telling you this is to do with how `javap` produces its output, not to do with what is or isn't present in the compiled `.class` file. But I don't have an answer for why `javap` doesn't print the word `default` in its output, so that is the question needing an answer. — kaya3, Jul 30 '21 at 19:35
@kaya3 well, that's all my question is about - why `default` is missing; however, I can't be sure, that it's due to `javap` and `javac`.. or maybe I should be sure? — Giorgi Tsiklauri, Jul 30 '21 at 19:37
Yes, I got that, and I'm telling you that I am sure `javap` is responsible for this, not `javac`. — kaya3, Jul 30 '21 at 19:38
@Eugene looks interesting.. so, it seems to be a `javap 11.0.2` bug then. — Giorgi Tsiklauri, Jul 30 '21 at 19:40
Note that methods are not generally implicitly public; rather, _all members_ of an interface are public. — chrylis -cautiouslyoptimistic-, Jul 30 '21 at 20:48
@chrylis-cautiouslyoptimistic- wrong. You can define `private` instance method. :) — Giorgi Tsiklauri, Jul 30 '21 at 21:08

score 4 · Accepted Answer · edited Jul 30 '21 at 19:41

4

Surely looks like a javap bug, see this defect. I've encountered a few more of these javap issues when new features where added, just FYI.

edited Jul 30 '21 at 19:41

kaya3

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answered Jul 30 '21 at 19:41

Eugene

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Upvoted; one catch though: "Affected versions: 8, 11.0.1, 12". They probably had it in the 11.0.2 as well. – Giorgi Tsiklauri Jul 30 '21 at 19:43
1

So, they've just included where it was fixed.. but not all the versions where it was present. :) – Giorgi Tsiklauri Jul 30 '21 at 19:46

Why, after compiling an interface, "default" method modifier is gone from "javap -v"?

1 Answers1