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Not implementing the JVM spec means it's not a JVM. It's that simple.

Rotten194 11y ago
OK but you're straying into pedantry. They have their own VM which runs bytecode generated by a translation layer. The only language supported by that translation layer is JVM bytecode. Therefore, they effectively have an implementation of the JVM.
- kuhn 11y ago
  Actually ART runs DEX bytecode not JVM bytecode so I'd argue it's not a JVM at all. By your definition anything that can translate Java to an intermediate representation is a JVM. Does that make LLVM a JVM? https://llvm.org/svn/llvm-project/java/trunk/docs/java-frontend.txt https://llvm.org/svn/llvm-project/java/trunk/docs/java-front...
  - AlphaSite 11y ago
    No, but ART's sole purpose is to run JVM translated programs. If you had another fm that run Java and other languages, you could argue that it is A JVM, but it is also a fm for what ever the language it runs.
  - wstrange 11y ago
    I am guessing Oracle's lawyers will argue that is indeed the case. Let's hope they do not prevail
    - gsnedders 11y ago
      They lost that argument against Google already.
- needusername 11y ago
  > OK but you're straying into pedantry. You are stripping words of their meaning. There is a precise definition of what JVM means. ART isn't close to that and doesn't try to do that. There's nothing wrong with that, just don't call it a JVM. You can translate Java into JavaScript and run it on a JavaScript VM. This doesn't make that JavaScript VM a JVM. Pointing out that a language isn't Java simply because it has curly braces isn't straying into pedantry. Pointing out that something isn't ice simply because it is solid isn't straying into pedantry.
  - s73v3r 11y ago
    They're not stripping anything of it's meaning; they're taking things to their logical conclusion. And there's really no way that you can claim the language used for Android development is not Java.
    - bitmapbrother 11y ago
      It's clear you don't understand how the ART VM works so why not research it instead of trying to argue how you think it works.
      - s73v3r 11y ago
        I know how it works. Claiming that someone who disagrees with you must not know how something works doesn't exactly prove your point.
    - needusername 11y ago
      > And there's really no way that you can claim the language used for Android development is not Java. Even if the language used for Android development is were Java that wouldn't make ART a JVM. JVM is a VM specification that is not tied to the source but the byte code. In several cases (eg. method lookup) there a significant differences between Java and JVM semantics. The language used for Android development is not Java. Again, there is a precise definition of what Java means (the language specification) and a test to verify what you have is Java (the TCK). ART/Android does not pass that test (it's not even close) and has no intention of doing so. For example Java semantics allow on the fly code generation. AFAIK ART/Android does not support this.
- bitmapbrother 11y ago
  I would argue who is being pedantic. They have a Java SDK so of course they're going to have a JVM bytecode->DEX bytecode translator, but that doesn't mean their VM is even remotely close to a JVM as they don't even share the same architecture.
s73v3r 11y ago
They're using the Java language. Therefore, something which interprets bytecode coming from it is a java virtual machine. It's that simple.
- bitmapbrother 11y ago
  You couldn't be more wrong. The ART VM processes DEX bytecode and it is not compatible with JVM bytecode. They also use different architectures.
  - s73v3r 11y ago
    Are you trying to say that the Java language isn't being used to write Android apps?
    - bitmapbrother 11y ago
      No, I'm saying the relevance of Java ends at the source level. When the app is converted to DEX bytecode and then compiled to native code there is no dependency on the language or JVM as you seem to think.
      - s73v3r 11y ago
        There clearly is, otherwise Google would have been able to update to Java 8 on Android by now.
        bitmapbrother 11y ago
        No, the reason Google isn't going to update to Java 8 is due to the litigation from Oracle. Google will likely transition to a new language so why invest time and money upgrading to a language they're going to abandon soon.

OK but you're straying into pedantry. They have their own VM which runs bytecode generated by a translation layer. The only language supported by that translation layer is JVM bytecode. Therefore, they effectively have an implementation of the JVM.

kuhn 11y ago
Actually ART runs DEX bytecode not JVM bytecode so I'd argue it's not a JVM at all. By your definition anything that can translate Java to an intermediate representation is a JVM. Does that make LLVM a JVM? https://llvm.org/svn/llvm-project/java/trunk/docs/java-frontend.txt https://llvm.org/svn/llvm-project/java/trunk/docs/java-front...
- AlphaSite 11y ago
  No, but ART's sole purpose is to run JVM translated programs. If you had another fm that run Java and other languages, you could argue that it is A JVM, but it is also a fm for what ever the language it runs.
- wstrange 11y ago
  I am guessing Oracle's lawyers will argue that is indeed the case. Let's hope they do not prevail
  - gsnedders 11y ago
    They lost that argument against Google already.
needusername 11y ago
> OK but you're straying into pedantry. You are stripping words of their meaning. There is a precise definition of what JVM means. ART isn't close to that and doesn't try to do that. There's nothing wrong with that, just don't call it a JVM. You can translate Java into JavaScript and run it on a JavaScript VM. This doesn't make that JavaScript VM a JVM. Pointing out that a language isn't Java simply because it has curly braces isn't straying into pedantry. Pointing out that something isn't ice simply because it is solid isn't straying into pedantry.
- s73v3r 11y ago
  They're not stripping anything of it's meaning; they're taking things to their logical conclusion. And there's really no way that you can claim the language used for Android development is not Java.
  - bitmapbrother 11y ago
    It's clear you don't understand how the ART VM works so why not research it instead of trying to argue how you think it works.
    - s73v3r 11y ago
      I know how it works. Claiming that someone who disagrees with you must not know how something works doesn't exactly prove your point.
  - needusername 11y ago
    > And there's really no way that you can claim the language used for Android development is not Java. Even if the language used for Android development is were Java that wouldn't make ART a JVM. JVM is a VM specification that is not tied to the source but the byte code. In several cases (eg. method lookup) there a significant differences between Java and JVM semantics. The language used for Android development is not Java. Again, there is a precise definition of what Java means (the language specification) and a test to verify what you have is Java (the TCK). ART/Android does not pass that test (it's not even close) and has no intention of doing so. For example Java semantics allow on the fly code generation. AFAIK ART/Android does not support this.
bitmapbrother 11y ago
I would argue who is being pedantic. They have a Java SDK so of course they're going to have a JVM bytecode->DEX bytecode translator, but that doesn't mean their VM is even remotely close to a JVM as they don't even share the same architecture.

s73v3r 11y ago

They're using the Java language. Therefore, something which interprets bytecode coming from it is a java virtual machine. It's that simple.

bitmapbrother 11y ago
You couldn't be more wrong. The ART VM processes DEX bytecode and it is not compatible with JVM bytecode. They also use different architectures.
- s73v3r 11y ago
  Are you trying to say that the Java language isn't being used to write Android apps?
  - bitmapbrother 11y ago
    No, I'm saying the relevance of Java ends at the source level. When the app is converted to DEX bytecode and then compiled to native code there is no dependency on the language or JVM as you seem to think.
    - s73v3r 11y ago
      There clearly is, otherwise Google would have been able to update to Java 8 on Android by now.
      - bitmapbrother 11y ago
        No, the reason Google isn't going to update to Java 8 is due to the litigation from Oracle. Google will likely transition to a new language so why invest time and money upgrading to a language they're going to abandon soon.