java [ options ] class [ argument ... ]
java [ options ] -jar file.jar [ argument ... ]
oldjava [ options ] class [ argument ... ]
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:
- The oldjava launcher does not support 1.2 security features, such as system policies. Java 1.1 platform security features are fully supported.
- The oldjava launcher does not support the extension mechanism. Extension packages can still be used 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. This allows programming techniques that are incompatible with the base class loader.
- 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 default behavior of the launcher is to execute bytecodes using a Just In Time compiler, or JIT. 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 set JAVA_COMPILER or java.compiler to the name of an alternative JIT. The launcher appends ".dll" to the JIT name and looks for a DLL file defining the JIT in the same directory as the launcher executable.
- Set the environment variable JAVA_COMPILER to "NONE", using the NT System Control Panel applet or the set command.
- Use -D option to set java.compiler to "NONE".
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 semicolons (;). 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 Configuration of JDK 1.2 Software under Solaris.
- -Dproperty=value
- Set a system property value.
- -jar
- 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.
- -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.
- -?
- -help
- Display usage information and exit.
- -X
- Display information about non-standard options and exit.