what the java virtual machine truely is?

Discussion in 'Java' started by 525, Mar 6, 2008.

  1. 525

    525 Guest

    Q: Can the java code run without java virtual machine ? When we
    instal the jdk, does the java virtual machine setup at the same
    time? What is the relationship between the fold jre and java
    virtual machine ?
    525, Mar 6, 2008
    #1
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  2. 525

    Lew Guest

    525 wrote:
    > Q: Can the java [sic] code run without java virtual machine ?


    Normally, no, but there are some compilers like GCJ (Gnu Compiler for J*va)
    that can run some Java code without a JVM.

    > When we instal the jdk [sic], does the java virtual machine setup at the same
    > time?


    It installs at the same time, in the form of the "java" command (java.exe on
    Windows), so I guess you could say its set up at the same time. There
    wouldn't be much point to the JDK without the JVM, after all.

    But simply installing the JDK doesn't *run* the JVM. That happens when you
    (directly or indirectly) invoke the 'java' command.

    > What is the relationship between the fold jre and java virtual machine ?


    What do you mean by the "fold" JRE?

    The JRE comprises the Java Virtual Machine and the rest of the Java Runtime
    Environment, including various bootstrap JARs and other components.

    Java, the programming language, is spelled with a capital "J".

    --
    Lew
    Lew, Mar 6, 2008
    #2
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  3. Lew wrote:
    > 525 wrote:
    >> Q: Can the java [sic] code run without java virtual machine ?

    >
    > Normally, no, but there are some compilers like GCJ (Gnu Compiler
    > for
    > J*va) that can run some Java code without a JVM.
    >
    >> When we instal the jdk [sic], does the java virtual machine setup
    >> at
    >> the same time?

    >
    > It installs at the same time, in the form of the "java" command
    > (java.exe on Windows), so I guess you could say its set up at the
    > same time. There wouldn't be much point to the JDK without the JVM,
    > after all.
    > But simply installing the JDK doesn't *run* the JVM. That happens
    > when you (directly or indirectly) invoke the 'java' command.
    >
    >> What is the relationship between the fold jre and java virtual
    >> machine ?

    >
    > What do you mean by the "fold" JRE?


    I'm guessing it's a typo for "full" (possibly assisted by a
    spell-checker that converted, say, "fuld" to "fold").

    >
    > The JRE comprises the Java Virtual Machine and the rest of the Java
    > Runtime Environment, including various bootstrap JARs and other
    > components.
    > Java, the programming language, is spelled with a capital "J".
    Mike Schilling, Mar 6, 2008
    #3
  4. Mike Schilling wrote:

    > Lew wrote:
    > > 525 wrote:
    > >
    > >> What is the relationship between the fold jre and java virtual
    > >> machine ?

    > >
    > > What do you mean by the "fold" JRE?

    >
    > I'm guessing it's a typo for "full" (possibly assisted by a
    > spell-checker that converted, say, "fuld" to "fold").
    >
    > >

    I thought he meant "folder". Either of the possibilties make sense to me
    :p
    --
    Sabine Dinis Blochberger

    Op3racional
    www.op3racional.eu
    Sabine Dinis Blochberger, Mar 6, 2008
    #4
  5. 525

    Roedy Green Guest

    On Wed, 5 Mar 2008 20:56:38 -0800 (PST), 525
    <> wrote, quoted or indirectly quoted someone
    who said :

    >Q: Can the java code run without java virtual machine ?

    That's a matter of semantics. It is possible to compile to native
    code. The vm is there only in the vaguest sense. see
    http://mindprod.com/jgloss/nativecompiler.html

    >When we
    >instal the jdk, does the java virtual machine setup at the same
    >time?


    The vm only exists while Java.exe is running.

    >What is the relationship between the fold jre and java
    >virtual machine ?


    When the JRE java.exe is running it is simulating the Java virtual
    machine. In other words, it makes your computer pretend to be an
    ideal Java computer that can run class files directly.


    --

    Roedy Green Canadian Mind Products
    The Java Glossary
    http://mindprod.com
    Roedy Green, Mar 6, 2008
    #5
  6. Lew wrote:
    > 525 wrote:
    >> When we instal the jdk [sic], does the java virtual machine setup at
    >> the same
    >> time?

    >
    > It installs at the same time, in the form of the "java" command
    > (java.exe on Windows), so I guess you could say its set up at the same
    > time. There wouldn't be much point to the JDK without the JVM, after all.


    Especially not since much (possible most) of the functionality in JDK
    is implemented in Java (tools.jar).

    Arne
    Arne Vajhøj, Mar 8, 2008
    #6
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