unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (OSF1-V5.1-alpha)
Page:
Section:
Apropos / Subsearch:
optional field



java(5)								      java(5)



NAME

  java,	javac, jre, jdb, javah,	javap, javadoc,	appletviewer, rmic, rmiregis-
  try, 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 documenta-
  tion 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
  filename extension .class which the compiler automatically adds when the
  class	is compiled. classname 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	com-
  pared	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>

  00		 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