java - Unix, Linux Command
NAME
java - Java application launcher
SYNOPSIS
java [
options ]
class [
argument ... ]
java [
options ]
-jar file.jar
[
argument ... ]
PARAMETERS
Tag | Description |
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 classs
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 support a
set of non-standard options that are
subject to
change in future releases.
Standard Options
Tag | Description |
|
-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.html
Tag | Description |
-agentpath:pathname[=options] | |
Load a native agent library by full pathname. For more
information, see JVMTI Agent Command Line Options at
http://java.sun.com/j2se.1.5.0/docs/guide/jvmti/jvmti.html
|
-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 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 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 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
packagecom.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
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 assertions in the specified
package and any subpackages. If the
argument 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
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
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 applications 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.instrument.
|
-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
Tag | Description |
-Xint |
Operates 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.
|
-Xdebug |
Start with support for JVMDI enabled. JVMDI has
been deprecated and is not used for
debugging in J2SE 5.0, so this option isnt
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: 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 |
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: 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 |
Performs strict class-file format checks.
For purposes of backwards compatibility,
the default format checks performed by the
Java 2 SDKs 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 |
Disables class garbage collection
|
-Xincgc |
Enable the incremental garbage collector. The incremental
garbage collector, which is off by default,
will reduce the occasional 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 |
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:
|
Tag | Description |
|
-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. 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.
Tag | Description |
-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.
|
-Xrunhprof[:help][:suboption=value,...]
| |
Enables cpu, heap, or monitor profiling.
This option is
typically 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.
Suns 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. Suns 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 JVMs own signal handlers. The
-Xrs command line option is available to address this issue.
When -Xrs is used on Suns 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 conseguences of specifying -Xrs:
|
Tag | Description |
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
See (or search
java.sun.com) for the following:
|