java(1) java(1)
NAME
java - Java application launcher
SYNOPSIS
java [ options ] class [ argument ... ]
java [ options ] -jar file.jar
[ argument ... ]
PARAMETERS
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 the
-jar option.
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 impletmentations of the virtual machines sup-
port a set of non-standard options that are subject to change in future
releases.
Standard Options
-client Selects the Java HotSpot Client VM. For more
information see Server-Class Machine Detection at
http://java.sun.com/j2se/1.5.0/docs/guide/vm/server-
class/
-server Selects the Java HotSpot Server VM. For more
information see Server-Class Machine Detection at
http://java.sun.com/j2se/1.5.0/docs/guide/vm/server-
class/
-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 at
http://java.sun.com/j2se.1.5.0/docs/guide/jvmti/jvmti/
-agentpath:pathname[=options]
Load a native agent library by full pathname. For more informa-
tion, see JVMTI Agent Command Line Options at
http://java.sun.com/j2se.1.5.0/docs/guide/jvmti/jvmti/
-classpath classpath
-cp classpath
Specifies 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 (.).
-Dproperty=value
Sets a system property value.
-d32
-d64 Specified whether the program is to be run in a 32-bit or 64-bit
environment if available.
Currently, only the Java HotSpot Server VM supports 64-bit operations
and the -server option is implicit with the use of -d64 . This is sub-
ject 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 enable 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 pack-
age in the current working directory. With one argument not end-
ing 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 packagecom.wombat.fruitbat (and any subpack-
ages), the following command could be used:
java -ea:com.wombat.fruitbat... <Main Class>
The -enableassertions and -ea switches apply to all s 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;
-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 asser-
tions in the specified package and any subpackages. If the argu-
ment is simply "...", the switch disables assertions in the
unnamed package in the rent working directory. With one argument
not ending in "...", the switch disables assertions in the spec-
ified 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 ss 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 archive. 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 applica-
tion's starting point. See the Jar tool reference page and the
Jar trail of the Java Tutorial 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.instru-
ment.
-verbose
-verbose:class
Displays information about each class loaded.
-verbose:gc
Reports on each garbage collection event.
-verbose:jni
Reports information about use of native methods and other Java
Native Interface activity.
-version
Displays version information and exit.
-showversion
Displays version information and continues.
-?
-help Displays usage information and exit.
-X Displays information about non-standard options and exit.
Non-Standard Options
-Xint Operates in interpreted-only mode. Compilation to
native code is disabled, and all bytecodes are exe-
cuted 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, run-
ning the method in interpreter mode until the back-
ground compilation is finished. The -Xbatch flag
disables background compilation so that compilation
of all methods proceeds as a foreground task until
completed.
-Xdebug Start with support for JVMDI enabled. JVMDI has
been deprecated and is not used for debugging in
J2SE 5.0, so this option isn't needed for debugging
in J2SE 5.0.
-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: Applica-
tions that use this option for the purpose of over-
riding a class in rt.jar should not be deployed as
doing so would contravene the Java 2 Runtime Envi-
ronment binary code license.
-Xbootclasspath/a:path
Specifies a colon-separated path of directories,
JAR archives, and ZIP archives to append to the
default bootstrap class path.
-Xbootclasspath/p:path
Specifies a colon-separated path of directories,
JAR archives, and ZIP archives to prepend in front
of the default bootstrap class path. Note: Appli-
cations 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 Performs strict class-file format checks. For pur-
poses of backwards compatibility, the default for-
mat 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 -Xfu-
ture 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 Disables class garbage collection
-Xincgc Enable the incremental garbage collector. The
incremental garbage collector, which is off by
default, will reduce the occasional garbage-collec-
tion pauses during program execution. The incremen-
tal garbage collector will at times execute concur-
rently with the program and during such times will
reduce the processor capacity available to the pro-
gram.
-Xloggc: file Report on each garbage collection event, as with
-verbose:gc, but log this data to file . In addi-
tion 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 Specifies the initial size of the memory allocation
pool. This value must be a multiple of 1024
greater than 1 MB. Append the letter k or K to
indicate kilobytes or the letter m or M to indicate
megabytes. The default value is 2MB. Examples:
-Xms6291456
-Xms6144k
-Xms6m
-Xmxn Specifies the maximum size, in bytes, of the memory allocation
pool. This value must be a multiple of 1024 greater than 2 MB.
Append the letter k or K to indicate kilobytes or the letter m
or M to indicate megabytes. The default value is 64MB. Exam-
ples:
-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 stan-
dard output. This option is provided as a utility that is use-
ful in program development and is not intended to be be used in
production systems.
-Xrunhprof[:help][:suboption=value,...]
Enables cpu, heap, or monitor profiling. This option is typi-
cally followed by a list of comma-separated suboption=value
pairs. Run the command java -Xrunhprof:help to obtain a list of
suboptions and their default values.
-Xrs Reduce usage of operating-system signals by Java virtual machine
(JVM).
n 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 abnor-
mal 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 fea-
ture of dumping thread stacks for debugging purposes. Sun's JVM
uses SIGQUIT to perform thread dumps.
Applications that embed 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 sig-
nals are not installed.
There are two conseguences 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. /TP -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.
SEE ALSO
javac(1), jdb(1), javah(1), jar(1),
See (or search java.sun.com) for the following:
The Java Extensions Framework @
http://java.sun.com/j2se/1.5.0/docs/guide/extensions/index/
Security Features @
http://java.sun.com/j2se/1.5.0/docs/guide/security/index/
23 June 2004 java(1)
Mac OS X 10.5 - Generated Sun Nov 11 20:33:22 EST 2007