/sys$common/syshlp/helplib.hlb JAVA, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Java expects the binary representation of the class to be in a
    file called file-name.CLASS, which is generated by compiling the
    corresponding source file with the JAVAC compiler. All Java class
    files end with the file name extension .CLASS, which the compiler
    automatically adds when the class is compiled. The class to be
    executed must contain a main method defined as follows:

    class Aclass {
        public static void main(String argv[]){
            . . .
        }
    }

    The Java interpreter executes the main method and then exits,
    unless main creates one or more threads. If any threads are
    created by main, then the JAVA command does not exit until the
    last thread exits.

    When you define your own classes, you need to specify their
    location. Use the logicals CLASSPATH (for a UNIX style directory
    path) or JAVA$CLASSPATH (for an OpenVMS style directory path) to
    do this.

    The CLASSPATH logical consists of a colon-separated list of
    directories that specifies the path. For example:

    .:/home/xyz/classes:/usr/local/java/classes

    Also, unlike on UNIX systems, you must also explicitly specify
    the system classes on CLASSPATH. For example:

       $ define/nolog CLASSPATH "/sys$common/java/lib/JDK116_CLASSES.ZIP:."

    The JAVA$CLASSPATH logical lets you define a classpath using
    OpenVMS filespecs.

    The following two sample statements accomplish the same result:

       $ DEF JAVA$CLASSPATH USER1$:[SMITH.KIT]JDK115_CLASSES.ZIP,[]

       $ DEF CLASSPATH "/user1$/smith/kit/jdk115_class.zip:."

    Note that:

    o  JAVA$CLASSPATH is a comma-separated list not enclosed in
       quotation marks.

    o  JAVA$CLASSPATH overrides CLASSPATH if CLASSPATH is defined.

                                   NOTE

       All Java files that are to be read by any of the Java tools
       or that serve as input class libraries (listed in CLASSPATH)
       must be in Stream_LF format.

       To determine the record format of your file, do the
       following:

           $ DIR/FULL MyFile.java

       And observe the line:

           Record format

       By default, a file initially created on an OpenVMS system,
       with a text editor for example, will have variable-length
       record format.

       Although, for example, a *.JAVA file with variable-length
       record format compiles correctly if it is error-free, the
       compiler does not produce proper diagnostic outputs if a
       compilation error occurs.

       To get a file into Stream_LF record format, do the
       following:

          $ CONVERT/FDL=SYS$INPUT input_file-name output_file-name
          FILE
              ALLOCATION              4
              BEST_TRY_CONTIGUOUS     yes
              EXTENSION               0
              ORGANIZATION            sequential
          RECORD
              BLOCK_SPAN              yes
              CARRIAGE_CONTROL        carriage_return
              FORMAT                  stream_LF
              SIZE                    0

       If you use a non-Stream_LF formatted file in a CLASSPATH,
       errors like this result:

           Unable to initialize threads: cannot find class java/lang/Thread

    Ordinarily, you compile source files with JAVAC, then run the
    program using JAVA; however, JAVA can be used to compile and
    run programs when the /CHECKSOURCE qualifier is used. As each
    class file is loaded, its modification date is compared to the
    modification date of the class source file. If the source was
    modified more recently, it is recompiled and the new class file
    is loaded. JAVA repeats this procedure until all the classes are
    correctly compiled and loaded.

    The interpreter can determine whether a class is legitimate
    through the mechanism of verification. Verification ensures that
    prior to their execution, class files do not violate any language
    constraints.

    You can specify the qualifiers for this command as one of the
    following:

    o  OpenVMS DCL style qualifiers

    o  Tru64 UNIX style switches

    To use the DCL style:

        $ DEFINE JAVA$USE_DCL 1
        $ @SYS$MANAGER:JAVA$SETUP

    To use the Tru64 UNIX style:

        $ DEASSIGN JAVA$USE_DCL
        $ @SYS$MANAGER:JAVA$SETUP

    Both styles are documented.