java
java(1) java(1)NAME
java - Java interpreterSYNOPSIS
java [ options ] class [ argument ... ] java [ options ] -jar file.jar [ argument ... ] PARAMETERS Options may be in any order. For a discussion of parame ters which apply to a specific option, see OPTIONS below. options Command-line options. See OPTIONS below. class Name of the class to be invoked. file.jar Name of the jar file to be invoked. Used only with the -jar option.DESCRIPTION
The java utility 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 have the following signature: public static void main(String args[]) The method must be declared public and static, it must not return any value, and it must accept a String array as a parameter. 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 speci fied, the first non-option argument is the name of a JAR archive containing class and resource files for the appli cation, 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 sup ported on the current runtime environment and will be sup ported in future releases. However, options below that are described as having been replaced by another one are obsolete and may be removed in a future release. An addi tional 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. Standard Options -client Selects the Java HotSpot Client VM. This is the default. -server Selects the Java HotSpot Server VM. -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 (:). Specify ing -classpath or -cp overrides any setting of the CLASSPATH environment variable. Used with java, the -classpath or -cp options only specify the class path for user classes. Used with oldjava, -classpath or -cp specify the class path for both user classes and boot strap classes. If -classpath and -cp are not used and CLASSPATH is not set, the user class path consists of the current directory (.). -debug This has been replaced by -Xdebug. -Dproperty=value Sets a system property value. -jar Executes 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 application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial for infor mation 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. -noclassgc This has been replaced by -Xnoclassgc. -msn This has been replaced by -Xms n. -mxn This has been replaced by -Xmx n. -ssn This has been replaced by -Xss n. -verbose -verbose:class Displays information about each class loaded. -verbosegc This has been replaced by -verbose:gc. -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 con tinues. -? -help Displays usage information and exit. -X Displays information about non-stan dard options and exit. Non-Standard Options -Xint Operates in interpreted-only mode. Compilation to native code is dis abled, 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. -Xbootclasspath:bootclasspath Specifies 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 and Java 2 Runtime Environment. -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. -Xdebug Starts with the debugger enabled. -Xfuture Performs strict class-file format checks. For purposes of backwards 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 for mat checks that enforce closer confor mance to the class-file format speci fication. 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 -Xmsn Specifies the initial size of the mem ory allocation pool. This value must be greater than 1000. To modify the meaning of n, append either the letter k for kilobytes or the letter m for megabytes. The default value is 2m. -Xmxn Specifies the maximum size of the mem ory allocation pool. This value must be greater than 1000. To modify the meaning of n, append either the letter k for kilobytes or the letter m for megabytes. The default value is 64m. -Xprof Profiles the running program, and sends profiling data to standard out put. 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 profil ing. This option is typically fol lowed by a list of comma-separated suboption=value pairs. Run the com mand java -Xrunhprof:help to obtain a list of suboptions and their default values. -Xssn Each Java thread has two stacks: one for Java code and one for C code. The -Xss option sets the maximum stack size that can be used by C code in a thread to n. Every thread that is spawned during the execution of the program passed to java has n as its C stack size. The default units for n are bytes and n must be > 1000 bytes. To modify the meaning of n, append either the letter k for kilobytes or the letter m for megabytes. The default stack size is determined by the Linux operating system upon which the Java platform is running. -Xrs Reduce usage of operating-system sig nals by Java virtual machine (JVM). Sun's JVM catches signals to implement shutdown hooks for abnormal JVM termi nation. The JVM uses SIGHUP, SIGINT, and SIGTERM to initiate the running of shutdown hooks. The JVM uses SIGQUIT to perform thread dumps. Applications that embed the JVM fre quently need to trap signals like SIG INT or SIGTERM, and in such cases there is the possibility of interfer ence between the applications' signal handlers and the JVM shutdown-hooks facility. To avoid such interference, the -Xrs option can be used to turn off the JVM shutdown-hooks feature. When -Xrs is used, the signal masks for SIGINT, SIGTERM, SIGHUP, and SIGQUIT are not changed by the JVM, and signal han dlers for these signals are not installed.ENVIRONMENT VARIABLES
CLASSPATH Used to provide the system with a path to user-defined classes. Directories are separated by colons. For example: .:/home/avh/classes:/usr/local/java/classesSEE ALSO
javac(1), jdb(1), javac(1), jar(1), set(1) See (or search java.sun.com) for the following: JDK File Structure @ http://java.sun.com/j2se/1.3/docs/tooldocs/linux/jdk files.html JAR Files @ http://java.sun.com/docs/books/tutorial/jar/NOTES
All the -X options are unstable. As noted in the OPTIONS section, some of the "standard" options are obsolete. 25 November 2000 java(1)