java [ threads flag ] [ options ] class [ argument ... ] java [ threads flag ] [ options ] -jar file.jar [ argument ... ] oldjava [ threads flag ] [ options ] class [ argument ... ]
- Command-line options.
- Name of the class to be invoked.
- Name of the jar file to be invoked. Used only with
- Argument passed to the main function.
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. This method must have the following signature:public static void main(String)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.
On Solaris systems, the java launcher tool comes in two variations: java, which implements all 1.2 features; and oldjava, a limited-feature launcher tool, which supports programming techniques that are incompatible with some 1.2 features. These are the differences between java and oldjava:
This command using oldjava
- The oldjava launcher does not support the extension mechanism, though it can, of course, use extension packages as class and resource archives.
- The oldjava launcher uses the bootstrap class loader for all classes, while the java launcher uses the bootstrap class loader only for bootstrap classes.
- With java, the -classpath and -cp options specify a search path for user classes, and cannot be used to specify locations for bootstrap classes. With oldjava the -classpath and -cp options specify locations for all classes, including botstrap classes.
Note that java and oldjava do not differ in their use of the CLASSPATH environment variable. Unless overridden by -classpath or -cp, CLASSPATH always specifies the location of user classes, but says nothing about the bootstrap classes.
- The oldjava launcher supports all the 1.2 security features. With oldjava, however, classes loaded from the class path will not have a protection domain and will therefore have all permissions which is true only for bootstrap classes with the java launcher.is equivalent to this command using javaoldjava -classpath <path> ...where in both cases <path> contains the file rt.jar. (See the JDK FIle Structure document for a description of rt.jar and its location in the JDK software.)java -Xbootclasspath:<path> -Djava.ext.dirs= ...
The default behavior of the launcher is to execute bytecodes using a Just-in-Time compiler, or JIT. The default compiler is located at jre/lib/sparc/libsunwjit.so. When a class is loaded, the JIT translates the class bytecodes into native machine code. Using a JIT causes a slight delay after each class load, but can improve overall program performance. In some cases, execution time will improve by a factor of ten.
If the JIT is disabled, bytecodes are executed directly by an interpreter. There are two ways to disable the JIT:
You can also use JAVA_COMPILER or java.compiler to the specify that an alternative JIT should be used:
- Set the environment variable JAVA_COMPILER to NONE, the setenv command.% setenv JAVA_COMPILER NONE
- Use the -D command-line option to set java.compiler to NONE.Using the command-line option overrides the setting of the JAVA_COMPILER environment variable.% java -Djava.compiler=NONE myappor% setenv JAVA_COMPILER fooThe letters lib are prepended to "foo" and an .so filename extension is added, so that, in this example, the virtual machine will search for a JIT compiler named libfoo.so. The search for the alternative compiler is made in the jre/lib/sparc directory and on the path specified by the LD_LIBRARY_PATH environment variable. If no such compiler is found, the virtual machine will default to using the interpreter.% java -Djava.compiler=foo myapp
The launcher has a set of standard options that are supported on the current runtime environment and will be supported in future releases. An additional set of non-standard options are specific to the current virtual machine implementation and are subject to change in the future. Non-standard options begin with -X
- -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.
Used with java or javaw, -classpath or -cp only specify the class path for user classes. Used with oldjava or oldjavaw, -classpath or -cp specify the class path for both user classes and bootstrap classes.
If -classpath and -cp are not used and CLASSPATH is not set, the user class path consists of the current directory (
For more information on class paths, see Setting the Class Path.
- Set a system property value.
- Execute a program encapsulated in a JAR archive. The first argument is the name of a JAR archive file instead of a startup class name. The startup class is specified by the Main-Class manifest header. The JAR file is the source of all user classes, and other user class path settings are ignored.
The oldjava and oldjavaw tools do not support the -jar option.
- Display information about each class loaded.
- Report on each garbage collection event.
- Report information about use of native methods and other Java Native Interface activity.
- Display version information and exit.
- Display usage information and exit.
- Display information about non-standard options and exit.
- 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 JDK 1.2 software.
- Start with the debugger enabled. The Java interpereter prints out a password for jdb's use. Refer to jdb description for more details and an example.
- Disable class garbage collection
- Specify the initial size of the memory allocation pool. This value must greather than 1000. To multiply the value by 1000, append the letter k. To multiply the value by 1 million, append the letter m. The default value is 1m
- Specify the maximum size of the memory allocation pool. This value must greather than 1000. To multiply the value by 1000, append the letter k. To multiply the value by 1 million, append the letter m. The default value is 16m.
- 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.
- Reduce the use of operating system signals.
- Perform additional check for Java Native Interface functions.