Runtime JDK 1.6)

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public void addShutdownHook (Thread hook)

Registers a new virtual-machine shutdown hook.

The Java virtual machine shuts down in response to two kinds of events:

The program exits normally, when the last non-daemon thread exits or when the exit (equivalently, System.exit) method is invoked, or
The virtual machine is terminated in response to a user interrupt, such as typing ^C, or a system-wide event, such as user logoff or system shutdown.

A shutdown hook is simply an initialized but unstarted thread. When the virtual machine begins its shutdown sequence it will start all registered shutdown hooks in some unspecified order and let them run concurrently. When all the hooks have finished it will then run all uninvoked finalizers if finalization-on-exit has been enabled. Finally, the virtual machine will halt. Note that daemon threads will continue to run during the shutdown sequence, as will non-daemon threads if shutdown was initiated by invoking the exit method.

Once the shutdown sequence has begun it can be stopped only by invoking the halt method, which forcibly terminates the virtual machine.

Once the shutdown sequence has begun it is impossible to register a new shutdown hook or de-register a previously-registered hook. Attempting either of these operations will cause an IllegalStateException to be thrown.

Shutdown hooks run at a delicate time in the life cycle of a virtual machine and should therefore be coded defensively. They should, in particular, be written to be thread-safe and to avoid deadlocks insofar as possible. They should also not rely blindly upon services that may have registered their own shutdown hooks and therefore may themselves in the process of shutting down. Attempts to use other thread-based services such as the AWT event-dispatch thread, for example, may lead to deadlocks.

Shutdown hooks should also finish their work quickly. When a program invokes exit the expectation is that the virtual machine will promptly shut down and exit. When the virtual machine is terminated due to user logoff or system shutdown the underlying operating system may only allow a fixed amount of time in which to shut down and exit. It is therefore inadvisable to attempt any user interaction or to perform a long-running computation in a shutdown hook.

Uncaught exceptions are handled in shutdown hooks just as in any other thread, by invoking the uncaughtException method of the thread's ThreadGroup object. The default implementation of this method prints the exception's stack trace to System.err and terminates the thread; it does not cause the virtual machine to exit or halt.

In rare circumstances the virtual machine may abort, that is, stop running without shutting down cleanly. This occurs when the virtual machine is terminated externally, for example with the SIGKILL signal on Unix or the TerminateProcess call on Microsoft Windows. The virtual machine may also abort if a native method goes awry by, for example, corrupting internal data structures or attempting to access nonexistent memory. If the virtual machine aborts then no guarantee can be made about whether or not any shutdown hooks will be run.

Parameters:
- hook - An initialized but unstarted {@link Thread} object
Throws:
- IllegalArgumentException - If the specified hook has already been registered, or if it can be determined that the hook is already running or has already been run
- IllegalStateException - If the virtual machine is already in the process of shutting down
- SecurityException - If a security manager is present and it denies {@link RuntimePermission}("shutdownHooks")
Since: 1.3
See Also: Runtime.removeShutdownHook(java.lang.Thread), Runtime.halt(int), Runtime.exit(int),

publicnative int availableProcessors ()

Returns the number of processors available to the Java virtual machine.

public Process exec (String command) throws IOException

Executes the specified string command in a separate process.

public Process exec (String cmdarray) throws IOException

Executes the specified command and arguments in a separate process.

public Process exec (String cmdarray, String envp) throws IOException

Executes the specified command and arguments in a separate process with the specified environment.

public Process exec (String cmdarray, String envp, File dir) throws IOException

Executes the specified command and arguments in a separate process with the specified environment and working directory.

Given an array of strings cmdarray, representing the tokens of a command line, and an array of strings envp, representing "environment" variable settings, this method creates a new process in which to execute the specified command.

This method checks that cmdarray is a valid operating system command. Which commands are valid is system-dependent, but at the very least the command must be a non-empty list of non-null strings.

If envp is null, the subprocess inherits the environment settings of the current process.

ProcessBuilder.start() is now the preferred way to start a process with a modified environment.

The working directory of the new subprocess is specified by dir. If dir is null, the subprocess inherits the current working directory of the current process.

If a security manager exists, its checkExec method is invoked with the first component of the array cmdarray as its argument. This may result in a SecurityException being thrown.

Starting an operating system process is highly system-dependent. Among the many things that can go wrong are:

The operating system program file was not found.
Access to the program file was denied.
The working directory does not exist.

In such cases an exception will be thrown. The exact nature of the exception is system-dependent, but it will always be a subclass of IOException.
Returns: A new {@link Process} object for managing the subprocess
Parameters:
- cmdarray - array containing the command to call and its arguments.
- envp - array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.
- dir - the working directory of the subprocess, or null if the subprocess should inherit the working directory of the current process.
Throws:
- SecurityException - If a security manager exists and its {@link SecurityManager#checkExec checkExec} method doesn't allow creation of the subprocess
- IOException - If an I/O error occurs
- NullPointerException - If cmdarray is null, or one of the elements of cmdarray is null, or one of the elements of envp is null
- IndexOutOfBoundsException - If cmdarray is an empty array (has length 0)
Since: 1.3
See Also: ProcessBuilder,

public Process exec (String command, String envp) throws IOException

Executes the specified string command in a separate process with the specified environment.

public Process exec (String command, String envp, File dir) throws IOException

Executes the specified string command in a separate process with the specified environment and working directory.

public void exit (int status)

Terminates the currently running Java virtual machine by initiating its shutdown sequence.

publicnative long freeMemory ()

Returns the amount of free memory in the Java Virtual Machine.

Returns the amount of free memory in the Java Virtual Machine.
Calling the
gc method may result in increasing the value returned
by freeMemory.
Returns: an approximation to the total amount of memory currently available for future allocated objects, measured in bytes.

publicnative void gc ()

Runs the garbage collector.

@Deprecated

public InputStream ~~getLocalizedInputStream~~ (InputStream in)

Creates a localized version of an input stream.

Creates a localized version of an input stream. This method takes an InputStream and returns an InputStream equivalent to the argument in all respects except that it is localized: as characters in the local character set are read from the stream, they are automatically converted from the local character set to Unicode.

If the argument is already a localized stream, it may be returned as the result.
Returns: a localized input stream
Parameters:
- in - InputStream to localize
See Also: InputStream, BufferedReader.BufferedReader(java.io.Reader), InputStreamReader.InputStreamReader(java.io.InputStream),

@Deprecated

public OutputStream ~~getLocalizedOutputStream~~ (OutputStream out)

Creates a localized version of an output stream.

Creates a localized version of an output stream. This method takes an OutputStream and returns an OutputStream equivalent to the argument in all respects except that it is localized: as Unicode characters are written to the stream, they are automatically converted to the local character set.

If the argument is already a localized stream, it may be returned as the result.
Returns: a localized output stream
Parameters:
- out - OutputStream to localize
See Also: OutputStream, BufferedWriter.BufferedWriter(java.io.Writer), OutputStreamWriter.OutputStreamWriter(java.io.OutputStream), PrintWriter.PrintWriter(java.io.OutputStream),

publicstatic Runtime getRuntime ()

Returns the runtime object associated with the current Java application.

Returns the runtime object associated with the current Java application.
Most of the methods of class Runtime are instance
methods and must be invoked with respect to the current runtime object.
Returns: the Runtime object associated with the current Java application.

public void halt (int status)

Forcibly terminates the currently running Java virtual machine.

public void load (String filename)

Loads the specified filename as a dynamic library.

Loads the specified filename as a dynamic library. The filename argument must be a complete path name, (for example Runtime.getRuntime().load("/home/avh/lib/libX11.so");).

First, if there is a security manager, its checkLink method is called with the filename as its argument. This may result in a security exception.

This is similar to the method Runtime.loadLibrary(String), but it accepts a general file name as an argument rather than just a library name, allowing any file of native code to be loaded.

The method System.load(String) is the conventional and convenient means of invoking this method.
Parameters:
- filename - the file to load.
Throws:
- SecurityException - if a security manager exists and its checkLink method doesn't allow loading of the specified dynamic library
- UnsatisfiedLinkError - if the file does not exist.
- NullPointerException - if filename is null
See Also: Runtime.getRuntime(), SecurityException, SecurityManager.checkLink(java.lang.String),

pack-privatesynchronized void load0 (Class fromClass, String filename)

public void loadLibrary (String libname)

Loads the dynamic library with the specified library name.

pack-privatesynchronized void loadLibrary0 (Class fromClass, String libname)

publicnative long maxMemory ()

Returns the maximum amount of memory that the Java virtual machine will attempt to use.

public boolean removeShutdownHook (Thread hook)

De-registers a previously-registered virtual-machine shutdown hook.

public void runFinalization ()

Runs the finalization methods of any objects pending finalization.

Runs the finalization methods of any objects pending finalization. Calling this method suggests that the Java virtual machine expend effort toward running the finalize methods of objects that have been found to be discarded but whose finalize methods have not yet been run. When control returns from the method call, the virtual machine has made a best effort to complete all outstanding finalizations.

The virtual machine performs the finalization process automatically as needed, in a separate thread, if the runFinalization method is not invoked explicitly.

The method System.runFinalization() is the conventional and convenient means of invoking this method.
See Also: Object.finalize(),

@Deprecated

publicstatic void ~~runFinalizersOnExit~~ (boolean value)

Enable or disable finalization on exit; doing so specifies that the finalizers of all objects that have finalizers that have not yet been automatically invoked are to be run before the Java runtime exits.

publicnative long totalMemory ()

Returns the total amount of memory in the Java virtual machine.

publicnative void traceInstructions (boolean on)

Enables/Disables tracing of instructions.

Enables/Disables tracing of instructions. If the boolean argument is true, this method suggests that the Java virtual machine emit debugging information for each instruction in the virtual machine as it is executed. The format of this information, and the file or other output stream to which it is emitted, depends on the host environment. The virtual machine may ignore this request if it does not support this feature. The destination of the trace output is system dependent.

If the boolean argument is false, this method causes the virtual machine to stop performing the detailed instruction trace it is performing.
Parameters:
- on - true to enable instruction tracing; false to disable this feature.

publicnative void traceMethodCalls (boolean on)

Enables/Disables tracing of method calls.

Enables/Disables tracing of method calls. If the boolean argument is true, this method suggests that the Java virtual machine emit debugging information for each method in the virtual machine as it is called. The format of this information, and the file or other output stream to which it is emitted, depends on the host environment. The virtual machine may ignore this request if it does not support this feature.

Calling this method with argument false suggests that the virtual machine cease emitting per-call debugging information.
Parameters:
- on - true to enable instruction tracing; false to disable this feature.