java(1)                                                                  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  dec‐
       laration 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 cur‐
       rent  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 @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/guides/vm/server-class.html

          -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 @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/guides/vm/server-class.html

          -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 @
             http://docs.oracle.com/javase/7/docs/plat‐
             form/jvmti/jvmti.html#starting.

          -agentpath:pathname[=options]
             Load a native agent library by full pathname. For more information,
             see JVMTI Agent Command Line Options @
             http://docs.oracle.com/javase/7/docs/plat‐
             form/jvmti/jvmti.html#starting.

          -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 base‐
             name of * is considered equivalent to specifying a list of all the
             files in the directory with the extension .jar or .JAR (a java pro‐
             gram 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 speci‐
             fied 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 vari‐
             able, 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 Sys‐
             tem.getenv("CLASSPATH").
             For more information on class paths, see Setting the Class Path @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/tools/index.html#classpath.

          -Dproperty=value
             Set a system property value.

          -d32

          -d64
             Request that the program to be run in a 32-bit or 64-bit environ‐
             ment, 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 opera‐
             tion, 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> ]

          -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.wom‐
             bat.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 pro‐
             vided to enable asserts in all system classes; see -disablesys‐
             temassertions below.  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 pro‐
             vided to enable asserts in all system classes; see -enablesys‐
             temassertions 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.

          -help or -?
             Display usage information and exit.

          -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 identi‐
             fies the class having the public static void main(String[] args)
             method that serves as your application's starting point. See the
             jar(1) and the Jar trail of the Java Tutorial @
             http://docs.oracle.com/javase/tutorial/deployment/jar for informa‐
             tion 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 @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/guides/jar/index.html.

          -javaagent:jarpath[=options]
             Load a Java programming language agent, see java.lang.instrument @
             http://docs.oracle.com/javase/7/docs/api/java/lang/instrument/pack‐
             age-summary.html.
          -jre-restrict-search
             Include user-private JREs in the version search.

          -no-jre-restrict-search
             Exclude user-private JREs in the version search.

          -showversion
             Display version information and continue. (See also -version.)

          -splash:imagepath
             Show splash screen with image specified by imagepath.

          -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. (See also -showversion.)

          -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 ver‐
             sion-id followed by a plus sign (+) , or two version-ranges com‐
             bined 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:"1.6.0_13 1.6*&1.6.0_10+"
             The meaning of the above is that the class or jar file requires
             either version 1.6.0_13, or a version with 1.6 as a version-id pre‐
             fix and that is not less than 1.6.0_10.. The exact syntax and defi‐
             nition 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 require‐
             ments 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.


   Non-Standard Options
          -X Display information about non-standard options and exit.

          -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 com‐
             piler 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 dis‐
             ables 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 platform JDK.
             Note: Applications that use this option for the purpose of overrid‐
             ing a class in rt.jar should not be deployed as doing so would con‐
             travene the Java 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 overrid‐
             ing a class in rt.jar should not be deployed as doing so would con‐
             travene the Java Runtime Environment binary code license.

          -Xcheck:jni
             Perform additional checks for Java Native Interface (JNI) func‐
             tions. Specifically, the Java Virtual Machine validates the parame‐
             ters passed to the JNI function as well as the runtime environment
             data before processing the JNI request. Any invalid data encoun‐
             tered 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 JDK'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 pro‐
             gram 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 sec‐
             onds) 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.

          -Xmnsize or -XX:NewSize
             Sets the size of the young generation (nursery).

          -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 @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/guides/vm/gc-ergonomics.html
             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 @
             http://docs.oracle.com/javase/7/docs/tech‐
             notes/guides/vm/gc-ergonomics.html
             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 Linux 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 pro‐
             gram development and is not intended to be used in production sys‐
             tems.

          -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 initi‐
             ate 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 termi‐
               nated.

          -Xssn
             Set thread stack size.

          -XX:AllocationPrefetchStyle=n
             Sets the style of prefetch used during allocation. default=2.

          -XX:+AggressiveOpts
             Enables aggressive optimization.

          -XX:+|-DisableAttachMechanism
             This option specifies whether tools (such as jmap and jconsole) are
             allowed to attach to the JVM. By default, this feature is disabled.
             That is, attaching is enabled. Example usage:
                   java -XX:+DisableAttachMechanism

          -XXLargePageSizeInBytes=n
             This option specifies the maximum size for large pages.

          -XX:MaxGCPauseMillis=n
             Sets a target for the maximum GC pause time.
             This is a soft goal, and the JVM will make its best effort to
             achieve it.

          -XX:NewSize
             Sets the size of the young generation (nursery). Sames as -Xmnsize.

          -XX:ParallelGCThreads=n
             Sets the number of GC threads in the parallel collectors.

          -XX:PredictedClassLoadCount=n
             This option requires that the UnlockExperimentalVMOptions flag be
             set first. Use the PredictedClassLoadCount flag if your application
             loads a lot of classes, and especially if class.forName() is used
             heavily. The recommended value is the number of classes loaded as
             shown in the output from -verbose:class.
             Example usage:
                   java -XX:+UnlockExperimentalVMOptions -XX:PredictedClassLoadCount=60013

          -XX:+PrintCompilation
             Prints verbose output from the HotSpot dynamic runtime compiler.

          -XX:+PrintGCDetails -XX:+PrintGCTimeStamps
             Prints garbage collection output along with time stamps.

          -XX:SoftRefLRUPolicyMSPerMB=0
             This flag enables aggressive processing of software references. Use
             this flag if HotSpot GC is impacted by the software reference
             count.

          -XX:TLABSize=n
             Thread local allocation buffers (TLAB) are enabled by default in
             HotSpot. HotSpot automatically sizes TLABs based on allocation pat‐
             terns. The -XX:TLABSize option allows fine-tuning the size of
             TLABs.

          -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.

          -XX:+|-UseCompressedOops
             Enables compressed references in 64-bit JVMs.
             This option is true by default.

          -XX:+UseConcMarkSweepGC or -XX:+UseG1GC
             These flags enable either the Concurrent Mark Sweep (CMS) or the G1
             garbage collectors.

          -XX:+|-UseLargePages
             Use this flag to enable large page support. Large pages are enabled
             by default on Solaris.

          -XX:+UseParallelOldGC
             Enables the parallel garbage collectors, which are optimized for
             throughput and average response time.

NOTES
       The -version:release command line option places no restrictions on the
       complexity of the release specification. However, only a restricted sub‐
       set 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:
             "1.6.0_10+"
             This would utilize any version greater than 1.6.0_10. This is use‐
             ful 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:
             "1.6.0_10+&1.6*"
          4. "Or" expressions of items 2. or 3. above. For example:
             "1.6.0_10+&1.6* 1.7+"
             Similar to item 2. this is useful when a change was introduced in a
             release (1.7) but also made available in updates to previous
             releases.

EXIT STATUS
       The following exit values are generally returned by the launcher, typi‐
       cally when the launcher is called with the wrong arguments, serious
       errors, or exceptions thrown from the Java Virtual Machine. However, a
       Java application may choose to return any value using the API call Sys‐
       tem.exit(exitValue).

          o 0: Successful completion

          o >0: An error occurred

SEE ALSO
          o javac(1)

          o jdb(1)

          o javah(1)

          o jar(1)

          o The Java Extensions Framework @
            http://docs.oracle.com/javase/7/docs/technotes/guides/exten‐
            sions/index.html

          o Security Features @
            http://docs.oracle.com/javase/7/docs/technotes/guides/secu‐
            rity/index.html.

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


                                   20 Mar 2012                           java(1)