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java(5)


NAME

  java, javac, jre, jdb, javah, javap, javadoc, appletviewer, rmic,
  rmiregistry, serialver, native2ascii, jar, javakey - The Java Development
  Kit tools


SYNOPSIS

  java [options] classname <args>

  java_g [options] classname <args>


DESCRIPTION

  This reference page describes the java command only.	The Java Development
  Kit (JDK) is part of the Java Virtual Machine (VM). If the JDK
  documentation was installed on your Tru64 UNIX system, you can view
  documentation on all of the JDK tools, and other Java reference material,
  at the following location:

	 /usr/share/doclib/java/index.html

  The java command invokes an interpreter that executes Java bytecodes. It
  executes Java class files created by a Java compiler, for instance, javac.


NOTES

  Any arguments that appear after classname on the command line are passed to
  the main method of the class.

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

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

  java executes the main method and then exits unless main creates one or
  more threads. If any threads are created by main then java doesn't exit
  until the last thread exits.

  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 -cs
  option 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
  has been 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 prior to their execution
  that class files do not violate any language constraints.

  java_g is a non-optimized version of java suitable for use with debuggers
  like jdb.


EXAMPLES

  The classname argument is the name of the class to be executed.  classname
  must be fully qualified by including its package in the name, for example:

       % java java.lang.String

  When you define your own classes, you need to specify their location.	 Use
  CLASSPATH to do this.	 CLASSPATH consists of a colon separated list of
  directories that specifies the path. For example:

       .:/home/xyz/classes

  The system always appends the location of the system classes onto the end
  of the class path unless you use the -classpath option to specify a path.


OPTIONS

  -debug
      Allows the Java debugger, jdb, to attach itself to this java session.
      When -debug is specified on the command line, java displays a password
      which must be used when starting the debugging session.

  -cs, -checksource
      When a compiled class is loaded, this option causes the modification
      time of the class bytecode file to be compared to that of the class
      source file.  If the source has been modified more recently, it is
      recompiled and the new class file is loaded.

  -classpath path
      Specifies the path java uses to look up classes.	Overrides the default
      or the CLASSPATH environment variable if it is set. Directories are
      separated by colons. Thus the general format for path is:

	   .:<your_path>

      For example:

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

  -mx x
      Sets the maximum size of the memory allocation pool (the garbage
      collected heap) to x. The default is 16 megabytes of memory.  x must be
      greater than or equal to 1000 bytes.

      By default, x is measured in bytes. You can specify x in either
      kilobytes or megabytes by appending the letter k for kilobytes or the
      letter m for megabytes.

  -ms x
      Sets the startup size of the memory allocation pool (the garbage
      collected heap) to x. The default is 1 megabyte of memory.  x must be >
      1000 bytes.

      By default, x is measured in bytes. You can specify x in either
      kilobytes or megabytes by appending the letter k for kilobytes or the
      letter m for megabytes.

  -noasyncgc
      Turns off asynchronous garbage collection. When activated no garbage
      collection takes place unless it is explicitly called or the program
      runs out of memory. Normally garbage collection runs as an asynchronous
      thread in parallel with other threads.

  -noclassgc
      Turns off garbage collection of Java classes. By default, the Java
      interpreter reclaims space for unused Java classes during garbage
      collection.

  -version
      Prints the build version information.

  -help
      Prints a usage message.

  -ss x
      Each Java thread has two stacks: one for Java code and one for C code.
      The -ss option sets the maximum stack size that can be used by C code
      in a thread to x. Every thread that is spawned during the execution of
      the program passed to java has x as its C stack size. The default units
      for x are bytes. The value of x must be greater than or equal to 1000
      bytes.

      You can modify the meaning of x by appending either the letter k for
      kilobytes or the letter m for megabytes. The default stack size is 128
      kilobytes (-ss 128k).

  -oss x
      Each Java thread has two stacks: one for Java code and one for C code.
      The -oss option sets the maximum stack size that can be used by Java
      code in a thread to x. Every thread that is spawned during the
      execution of the program passed to java has x as its Java stack size.
      The default units for x are bytes. The value of x must be greater than
      or equal to 1000 bytes.

      You can modify the meaning of x by appending either the letter k for
      kilobytes or the letter m for megabytes. The default stack size is 400
      kilobytes (-oss 400k).

  -t  Prints a trace of the instructions executed (java_g only).

  -v, -verbose
      Causes java to print a message to stdout each time a class file is
      loaded.

  -verify
      Runs the verifier on all code.

  -verifyremote
      Runs the verifier on all code that is loaded into the system via a
      classloader.  -verifyremote is the default for the interpreter.

  -noverify
      Turns verification off.

  -verbosegc
      Causes the garbage collector to print out messages whenever it frees
      memory.

  -DpropertyName=newValue
      Redefines a property value.  propertyName is the name of the property
      whose value you want to change and newValue is the value to change it
      to. For example, this command line

	   % java -Dawt.button.color=green ...

      sets the value of the property awt.button.color to "green".  java
      accepts any number of -D options on the command line.


ENVIRONMENT VARIABLES

  CLASSPATH
      Used to provide the system a path to user-defined classes. Directories
      are separated by colons, for example,

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


SEE ALSO

  If the JDK documentation was installed on your Tru64 UNIX system, you can
  view it at the following location:

       /usr/share/doclib/java/index.html

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