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
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 sup‐
port 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 informa‐
tion, 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 speci‐
fied directory, even hidden ones, are included in the list. A class‐
path 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("CLASS‐
PATH").
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 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 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[:"..." | : ]
-ea[:"..." | : ]
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...
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[:"..." | : ]
-da[:"..." | : ]
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
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 pub‐
lic 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 ver‐
sion 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 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 pre‐
fix and that is not less than 1.5.1_02. The exact syntax and defini‐
tion of version strings may be found in Appendix A of the Java Net‐
work 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.
-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 inter‐
preter. 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 inter‐
preter mode until the background compilation is finished. The
-Xbatch flag disables background compilation so that compila‐
tion of all methods proceeds as a foreground task until com‐
pleted.
-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 run‐
time 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 back‐
wards 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 specifica‐
tion. Developers are encouraged to use this flag when develop‐
ing 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 pre‐
vent memory recovery from loaded classes thus increasing over‐
all 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 exe‐
cution. The incremental garbage collector will at times exe‐
cute 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 trun‐
cated 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 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 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 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 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 avail‐
able 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 some‐
times 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)
Monday, January 24, 2011
java
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