java [ options ] class [ argument ... ]
java [ options ] -jar file.jar [ argument ... ]
javaw [ options ] class [ argument ... ]
javaw [ options ] -jar file.jar [ argument ... ]
optionsclassfile.jar-jar.argumentThe 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 f iles 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.
The javaw command is identical to java, except that with javaw there is no associated console window. Use javaw when you don't want a command prompt window to appear. The javaw launcher will, however, display a dialog box with error information if a launch fails for some reason.
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 default Java HotSpot VMs provide a set of non-standard options that are subject to change in future releases.
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
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. This is subject to change in a future release.
For default VM selection, see Server-Class Machine Detection
-agentlib:hprof
-agentlib:jdwp=help
-agentlib:hprof=help
For more information, see JVMTI Agent Command Line Options.
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.
java -Dfoo="some string" SomeClass
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.
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.
When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.
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 adding 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 prefix and that is not less than 1.6.0_10. 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.
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.
Examples:
-Xms6291456
-Xms6144k
-Xms6m
Examples:
-Xmx83886080
-Xmx81920k
-Xmx80m
In J2SE 1.3.0, 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.
The JVM watches for console control events to implement shutdown hooks for abnormal JVM termination. Specifically, the JVM registers a console control handler which begins shutdown-hook processing and returns TRUE for CTRL_C_EVENT, CTRL_CLOSE_EVENT, CTRL_LOGOFF_EVENT, and CTRL_SHUTDOWN_EVENT.
The JVM uses a similar mechanism to implement the pre-1.2 feature of dumping thread stacks for debugging purposes. Sun's JVM uses CTRL_BREAK_EVENT to perform thread dumps.
If the JVM is run as a service (for example, the servlet engine for a web server), it can receive CTRL_LOGOFF_EVENT but should not initiate shutdown since the operating system will not actually terminate the process. To avoid possible interference such as this, the -Xrs command-line option has been added beginning with J2SE 1.3.1. When the -Xrs option is used on Sun's JVM, the JVM does not install a console control handler, implying that it does not watch for or process CTRL_C_EVENT, CTRL_CLOSE_EVENT, CTRL_LOGOFF_EVENT, or CTRL_SHUTDOWN_EVENT.
There are two consequences of specifying -Xrs:
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:
"1.6.0_10+"Would utilize any version greater than 1.6.0_10. This is useful for a case where an interface was introduced (or a bug fixed) in the release specified.
"1.6.0_10+ & 1.6*"
"1.6.0_10+ & 1.6* 1.7+"This is 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.
The following exit values are generally returned by the launcher, typically
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
System.exit(exitValue).
0: Successful completion.>0: An error occurred.