java(1)                    OpenBSD Reference Manual                    java(1)



NAME
       java - the Java application launcher

SYNOPSIS
           java [ options ] class [ argument ... ]
           java [ options ] -jar file.jar [ argument ... ]


             options
                Command-line options.

             class
                Name of the class to be invoked.

             file.jar
                Name of the jar file to be invoked. Used only with -jar.

             argument
                Argument passed to the main function.


DESCRIPTION
       The java tool launches a Java application. It does this by starting a
       Java runtime environment, loading a specified class, and invoking that
       class's main method.

       The method must be declared public and static, it must not return any
       value, and it must accept a String array as a parameter. The method
       declaration must look like the following:

           public static void main(String args[])


       By default, the first non-option argument is the name of the class to
       be invoked. A fully-qualified class name should be used. If the -jar
       option is specified, the first non-option argument is the name of a JAR
       archive containing class and resource files for the application, with
       the startup class indicated by the Main-Class manifest header.

       The Java runtime searches for the startup class, and other classes
       used, in three sets of locations: the bootstrap class path, the
       installed extensions, and the user class path.

       Non-option arguments after the class name or JAR file name are passed
       to the main function.

OPTIONS
       The launcher has a set of standard options that are supported on the
       current runtime environment and will be supported in future releases.
       In addition, the current implementations of the virtual machines
       support a set of non-standard options that are subject to change in
       future releases.

Standard Options
          -client

          Select the Java HotSpot Client VM. A 64-bit capable jdk currently
          ignores this option and instead uses the Java Hotspot Server VM.

          For default VM selection, see Server-Class Machine Detection

          -server

          Select the Java HotSpot Server VM. On a 64-bit capable jdk only the
          Java Hotspot Server VM is supported so the -server option is
          implicit.

          For default VM selection, see Server-Class Machine Detection

          -agentlib:libname[=options]
             Load native agent library libname, e.g.

          -agentlib:hprof

          -agentlib:jdwp=help

          -agentlib:hprof=help

          For more information, see JVMTI Agent Command Line Options.

          -agentpath:pathname[=options]
             Load a native agent library by full pathname. For more
             information, see JVMTI Agent Command Line Options.

          -classpath classpath

          -cp classpath
             Specify a list of directories, JAR archives, and ZIP archives to
             search for class files. Class path entries are separated by
             colons (:). Specifying -classpath or -cp overrides any setting of
             the CLASSPATH environment variable.

          If -classpath and -cp are not used and CLASSPATH is not set, the
          user class path consists of the current directory (.).

          As a special convenience, a class path element containing a basename
          of * is considered equivalent to specifying a list of all the files
          in the directory with the extension .jar or .JAR (a java program
          cannot tell the difference between the two invocations).
          For example, if directory foo contains a.jar and b.JAR, then the
          class path element foo/* is expanded to a A.jar:b.JAR, except that
          the order of jar files is unspecified. All jar files in the
          specified directory, even hidden ones, are included in the list. A
          classpath entry consisting simply of * expands to a list of all the
          jar files in the current directory. The CLASSPATH environment
          variable, where defined, will be similarly expanded. Any classpath
          wildcard expansion occurs before the Java virtual machine is started
          -- no Java program will ever see unexpanded wildcards except by
          querying the environment. For example; by invoking
          System.getenv("CLASSPATH").

          For more information on class paths, see Setting the Class Path.

          -Dproperty=value
             Set a system property value.

          -d32

          -d64
             Request that the program to be run in a 32-bit or 64-bit
             environment, respectively. If the requested environment is not
             installed or is not supported, an error is reported.

          Currently only the Java HotSpot Server VM supports 64-bit operation,
          and the "-server" option is implicit with the use of -d64. And the
          "-client" option is ignored with the use of -d64. This is subject to
          change in a future release.

          If neither -d32 nor -d64 is specified, the default is to run in a
          32-bit environment, except for 64-bit only systems. This is subject
          to change in a future release.

          -enableassertions[:<package name>"..." | :<class name> ]

          -ea[:<package name>"..." | :<class name> ]
             Enable assertions. Assertions are disabled by default.

          With no arguments, enableassertions or -ea enables assertions. With
          one argument ending in "...", the switch enables assertions in the
          specified package and any subpackages. If the argument is simply
          "...", the switch enables assertions in the unnamed package in the
          current working directory. With one argument not ending in "...",
          the switch enables assertions in the specified class.

          If a single command line contains multiple instances of these
          switches, they are processed in order before loading any classes.
          So, for example, to run a program with assertions enabled only in
          package com.wombat.fruitbat (and any subpackages), the following
          command could be used:
          java -ea:com.wombat.fruitbat... <Main Class>

          The -enableassertions and -ea switches apply to all class loaders
          and to system classes (which do not have a class loader). There is
          one exception to this rule: in their no-argument form, the switches
          do not apply to system. This makes it easy to turn on asserts in all
          classes except for system classes. A separate switch is provided to
          enable asserts in all system classes; see -enablesystemassertions
          below.

          -disableassertions[:<package name>"..." | :<class name> ]

          -da[:<package name>"..." | :<class name> ]
             Disable assertions. This is the default.

          With no arguments, disableassertions or -da disables assertions.
          With one argument ending in "...", the switch disables assertions in
          the specified package and any subpackages. If the argument is simply
          "...", the switch disables assertions in the unnamed package in the
          current working directory. With one argument not ending in "...",
          the switch disables assertions in the specified class.

          To run a program with assertions enabled in package
          com.wombat.fruitbat but disabled in class
          com.wombat.fruitbat.Brickbat, the following command could be used:
          java -ea:com.wombat.fruitbat... -da:com.wombat.fruitbat.Brickbat <Main Class>

          The -disableassertions and -da switches apply to all class loaders
          and to system classes (which do not have a class loader). There is
          one exception to this rule: in their no-argument form, the switches
          do not apply to system. This makes it easy to turn on asserts in all
          classes except for system classes. A separate switch is provided to
          enable asserts in all system classes; see -disablesystemassertions
          below.

          -enablesystemassertions

          -esa
             Enable asserts in all system classes (sets the default assertion
             status for system classes to true).

          -disablesystemassertions

          -dsa
             Disables asserts in all system classes.

          -jar
             Execute a program encapsulated in a JAR file. The first argument
             is the name of a JAR file instead of a startup class name. In
             order for this option to work, the manifest of the JAR file must
             contain a line of the form Main-Class: classname. Here, classname
             identifies the class having the
             public static void main(String[] args) method that serves as your
             application's starting point. See the Jar tool reference page and
             the Jar trail of the Java Tutorial @
             http://java.sun.com/docs/books/tutorial/jar for information about
             working with Jar files and Jar-file manifests.

          When you use this option, the JAR file is the source of all user
          classes, and other user class path settings are ignored.

          Note that JAR files that can be run with the "java -jar" option can
          have their execute permissions set so they can be run without using
          "java -jar". Refer to Java Archive (JAR) Files.

          -javaagent:jarpath[=options]
             Load a Java programming language agent, see java.lang.instrument.

          -verbose

          -verbose:class
             Display information about each class loaded.

          -verbose:gc
             Report on each garbage collection event.

          -verbose:jni
             Report information about use of native methods and other Java
             Native Interface activity.

          -version
             Display version information and exit.

          -version:release
             Specifies that the version specified by release is required by
             the class or jar file specified on the command line. If the
             version of the java command invoked does not meet this
             specification and an appropriate implementation is found on the
             system, the appropriate implementation will be used.

          release not only can specify an exact version, but can also specify
          a list of versions called a version string. A version string is an
          ordered list of version ranges separated by spaces. A version range
          is either a version-id, a version-id followed by a star (*), a
          version-id followed by a plus sign (+) , or two version-ranges
          combined using an ampersand (&). The star means prefix match, the
          plus sign means this version or greater, and the ampersand means the
          logical anding of the two version-ranges. For example:
          -version:"1.5.0_04 1.5*&1.5.1_02+"
          The meaning of the above is that the class or jar file requires
          either version 1.5.0_02, or a version with 1.5 as a version-id
          prefix and that is not less than 1.5.1_02. The exact syntax and
          definition of version strings may be found in Appendix A of the Java
          Network Launching Protocol & API Specification (JSR-56).

          For jar files, the usual preference is to specify version
          requirements in the jar file manifest rather than on the command
          line.

          See the following NOTES section for important policy information on
          the use of this option.

          -showversion
             Display version information and continue.

          -?

          -help
             Display usage information and exit.

          -X Display information about non-standard options and exit.


   Non-Standard Options
             -Xint
                Operate in interpreted-only mode. Compilation to native code
                is disabled, and all bytecodes are executed by the
                interpreter. The performance benefits offered by the Java
                HotSpot VMs' adaptive compiler will not be present in this
                mode.

             -Xbatch
                Disable background compilation. Normally the VM will compile
                the method as a background task, running the method in
                interpreter mode until the background compilation is finished.
                The -Xbatch flag disables background compilation so that
                compilation of all methods proceeds as a foreground task until
                completed.

             -Xbootclasspath:bootclasspath
                Specify a colon-separated list of directories, JAR archives,
                and ZIP archives to search for boot class files. These are
                used in place of the boot class files included in the Java 2
                SDK. Note: Applications that use this option for the purpose
                of overriding a class in rt.jar should not be deployed as
                doing so would contravene the Java 2 Runtime Environment
                binary code license.

             -Xbootclasspath/a:path
                Specify a colon-separated path of directires, JAR archives,
                and ZIP archives to append to the default bootstrap class
                path.

             -Xbootclasspath/p:path
                Specify a colon-separated path of directires, JAR archives,
                and ZIP archives to prepend in front of the default bootstrap
                class path. Note: Applications that use this option for the
                purpose of overriding a class in rt.jar should not be deployed
                as doing so would contravene the Java 2 Runtime Environment
                binary code license.

             -Xcheck:jni
                Perform additional checks for Java Native Interface (JNI)
                functions. Specifically, the Java Virtual Machine validates
                the parameters passed to the JNI function as well as the
                runtime environment data before processing the JNI request.
                Any invalid data encountered indicates a problem in the native
                code, and the Java Virtual Machine will terminate with a fatal
                error in such cases. Expect a performance degradation when
                this option is used.

             -Xfuture
                Perform strict class-file format checks. For purposes of
                backwards compatibility, the default format checks performed
                by the Java 2 SDK's virtual machine are no stricter than the
                checks performed by 1.1.x versions of the JDK software. The
                -Xfuture flag turns on stricter class-file format checks that
                enforce closer conformance to the class-file format
                specification. Developers are encouraged to use this flag when
                developing new code because the stricter checks will become
                the default in future releases of the Java application
                launcher.

             -Xnoclassgc
                Disable class garbage collection. Use of this option will
                prevent memory recovery from loaded classes thus increasing
                overall memory usage. This could cause OutOfMemoryError to be
                thrown in some applications.

             -Xincgc
                Enable the incremental garbage collector. The incremental
                garbage collector, which is off by default, will reduce the
                occasional long garbage-collection pauses during program
                execution. The incremental garbage collector will at times
                execute concurrently with the program and during such times
                will reduce the processor capacity available to the program.

             -Xloggc:file
                Report on each garbage collection event, as with -verbose:gc,
                but log this data to file. In addition to the information
                -verbose:gc gives, each reported event will be preceeded by
                the time (in seconds) since the first garbage-collection
                event.

             Always use a local file system for storage of this file to avoid
             stalling the JVM due to network latency. The file may be
             truncated in the case of a full file system and logging will
             continue on the truncated file. This option overrides -verbose:gc
             if both are given on the command line.

             -Xmsn
                Specify the initial size, in bytes, of the memory allocation
                pool. This value must be a multiple of 1024 greater than 1MB.
                Append the letter k or K to indicate kilobytes, or m or M to
                indicate megabytes. The default value is chosen at runtime
                based on system configuration. For more information, see
                HotSpot Ergonomics
                Examples:


                       -Xms6291456
                       -Xms6144k
                       -Xms6m


             -Xmxn
                Specify the maximum size, in bytes, of the memory allocation
                pool. This value must a multiple of 1024 greater than 2MB.
                Append the letter k or K to indicate kilobytes, or m or M to
                indicate megabytes. The default value is chosen at runtime
                based on system configuration. For more information, see
                HotSpot Ergonomics
                Examples:


                       -Xmx83886080
                       -Xmx81920k
                       -Xmx80m

             On Solaris 7 and Solaris 8 SPARC platforms, the upper limit for
             this value is approximately 4000m minus overhead amounts. On
             Solaris 2.6 and x86 platforms, the upper limit is approximately
             2000m minus overhead amounts. On Bsd platforms, the upper limit
             is approximately 2000m minus overhead amounts.

             -Xprof
                Profiles the running program, and sends profiling data to
                standard output. This option is provided as a utility that is
                useful in program development and is not intended to be be
                used in production systems.

             -Xrs
                Reduces use of operating-system signals by the Java virtual
                machine (JVM).

             In a previous release, the Shutdown Hooks facility was added to
             allow orderly shutdown of a Java application. The intent was to
             allow user cleanup code (such as closing database connections) to
             run at shutdown, even if the JVM terminates abruptly.

             Sun's JVM catches signals to implement shutdown hooks for
             abnormal JVM termination. The JVM uses SIGHUP, SIGINT, and
             SIGTERM to initiate the running of shutdown hooks.

             The JVM uses a similar mechanism to implement the pre-1.2 feature
             of dumping thread stacks for debugging purposes. Sun's JVM uses
             SIGQUIT to perform thread dumps.

             Applications embedding the JVM frequently need to trap signals
             like SIGINT or SIGTERM, which can lead to interference with the
             JVM's own signal handlers. The -Xrs command-line option is
             available to address this issue. When -Xrs is used on Sun's JVM,
             the signal masks for SIGINT, SIGTERM, SIGHUP, and SIGQUIT are not
             changed by the JVM, and signal handlers for these signals are not
             installed.

             There are two consequences of specifying -Xrs:

                o SIGQUIT thread dumps are not available.

                o User code is responsible for causing shutdown hooks to run,
                  for example by calling System.exit() when the JVM is to be
                  terminated.

             -Xssn
                Set thread stack size.

             -XX:+UseAltSigs
                The VM uses SIGUSR1 and SIGUSR2 by default, which can
                sometimes conflict with applications that signal-chain SIGUSR1
                and SIGUSR2. The -XX:+UseAltSigs option will cause the VM to
                use signals other than SIGUSR1 and SIGUSR2 as the default.


NOTES
       The -version:release command line option places no restrictions on the
       complexity of the release specification. However, only a restricted
       subset of the possible release specifications represent sound policy
       and only these are fully supported. These policies are:

          1. Any version, represented by not using this option.

          2. Any version greater than an arbitrarily precise version-id. For
             example:
             "1.5.0_03+"

          Would utilize any version greater than 1.5.0_03. This is useful for
          a case where an interface was introduced (or a bug fixed) in the
          release specified.

          3. A version greater than an arbitrarily precise version-id, bounded
             by the upper bound of that release family. For example:
             "1.5.0_03+&1.5*"

          4. "Or" expressions of items 2. or 3. above. For example:
             "1.4.2_05+&1.4* 1.5+"
             Similar to item 2. this is useful when a change was introduced in
             a release (1.5) but also made available in updates to previous
             releases.


SEE ALSO
          o javac - the Java programming language compiler

          o jdb - Java Application Debugger

          o javah - C Header and Stub File Generator

          o jar - JAR Archive Tool

          o The Java Extensions Framework

          o Security Features.

          o HotSpot VM Specific Options @
            http://java.sun.com/docs/hotspot/VMOptions.html.


                                  07 Aug 2006                          java(1)
