https://openjdk.java.net/ 
/*
 * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import java.io.*;
import java.util.StringTokenizer;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;


Every Java application has a single instance of class
Runtime that allows the application to interface with
the environment in which the application is running. The current
runtime can be obtained from the getRuntime method.


An application cannot create its own instance of this class.

Author: unascribed
See Also:
Since:  JDK1.0
/**
 * Every Java application has a single instance of class
 * <code>Runtime</code> that allows the application to interface with
 * the environment in which the application is running. The current
 * runtime can be obtained from the <code>getRuntime</code> method.
 * <p>
 * An application cannot create its own instance of this class.
 *
 * @author  unascribed
 * @see     java.lang.Runtime#getRuntime()
 * @since   JDK1.0
 */

public class Runtime {
    private static Runtime currentRuntime = new Runtime();

    
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.
/**
     * Returns the runtime object associated with the current Java application.
     * Most of the methods of class <code>Runtime</code> are instance
     * methods and must be invoked with respect to the current runtime object.
     *
     * @return  the <code>Runtime</code> object associated with the current
     *          Java application.
     */
    public static Runtime getRuntime() {
        return currentRuntime;
    }

    
Don't let anyone else instantiate this class 
/** Don't let anyone else instantiate this class */
    private Runtime() {}

    
Terminates the currently running Java virtual machine by initiating its
shutdown sequence.  This method never returns normally.  The argument
serves as a status code; by convention, a nonzero status code indicates
abnormal termination.

 The virtual machine's shutdown sequence consists of two phases. In the first phase all registered shutdown hooks, if any, are started in some unspecified order and allowed to run concurrently until they finish. In the second phase all uninvoked finalizers are run if finalization-on-exit has been enabled. Once this is done the virtual machine 
halts. 
 If this method is invoked after the virtual machine has begun its
shutdown sequence then if shutdown hooks are being run this method will
block indefinitely.  If shutdown hooks have already been run and on-exit
finalization has been enabled then this method halts the virtual machine
with the given status code if the status is nonzero; otherwise, it
blocks indefinitely.

 The System.exit method is the
conventional and convenient means of invoking this method. 


Params:
  • status – 
        Termination status.  By convention, a nonzero status code
        indicates abnormal termination.
Throws:
See Also:
/**
     * Terminates the currently running Java virtual machine by initiating its
     * shutdown sequence.  This method never returns normally.  The argument
     * serves as a status code; by convention, a nonzero status code indicates
     * abnormal termination.
     *
     * <p> The virtual machine's shutdown sequence consists of two phases.  In
     * the first phase all registered {@link #addShutdownHook shutdown hooks},
     * if any, are started in some unspecified order and allowed to run
     * concurrently until they finish.  In the second phase all uninvoked
     * finalizers are run if {@link #runFinalizersOnExit finalization-on-exit}
     * has been enabled.  Once this is done the virtual machine {@link #halt
     * halts}.
     *
     * <p> If this method is invoked after the virtual machine has begun its
     * shutdown sequence then if shutdown hooks are being run this method will
     * block indefinitely.  If shutdown hooks have already been run and on-exit
     * finalization has been enabled then this method halts the virtual machine
     * with the given status code if the status is nonzero; otherwise, it
     * blocks indefinitely.
     *
     * <p> The <tt>{@link System#exit(int) System.exit}</tt> method is the
     * conventional and convenient means of invoking this method. <p>
     *
     * @param  status
     *         Termination status.  By convention, a nonzero status code
     *         indicates abnormal termination.
     *
     * @throws SecurityException
     *         If a security manager is present and its <tt>{@link
     *         SecurityManager#checkExit checkExit}</tt> method does not permit
     *         exiting with the specified status
     *
     * @see java.lang.SecurityException
     * @see java.lang.SecurityManager#checkExit(int)
     * @see #addShutdownHook
     * @see #removeShutdownHook
     * @see #runFinalizersOnExit
     * @see #halt(int)
     */
    public void exit(int status) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkExit(status);
        }
        Shutdown.exit(status);
    }

    
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. 


Params:
  • hook – 
         An initialized but unstarted Thread object
Throws:
See Also:
Since:1.3
/**
     * Registers a new virtual-machine shutdown hook.
     *
     * <p> The Java virtual machine <i>shuts down</i> in response to two kinds
     * of events:
     *
     *   <ul>
     *
     *   <p> <li> The program <i>exits</i> normally, when the last non-daemon
     *   thread exits or when the <tt>{@link #exit exit}</tt> (equivalently,
     *   <tt>{@link System#exit(int) System.exit}</tt>) method is invoked, or
     *
     *   <p> <li> The virtual machine is <i>terminated</i> in response to a
     *   user interrupt, such as typing <tt>^C</tt>, or a system-wide event,
     *   such as user logoff or system shutdown.
     *
     *   </ul>
     *
     * <p> A <i>shutdown hook</i> 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 <tt>{@link #exit exit}</tt>
     * method.
     *
     * <p> Once the shutdown sequence has begun it can be stopped only by
     * invoking the <tt>{@link #halt halt}</tt> method, which forcibly
     * terminates the virtual machine.
     *
     * <p> 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
     * <tt>{@link IllegalStateException}</tt> to be thrown.
     *
     * <p> 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.
     *
     * <p> Shutdown hooks should also finish their work quickly.  When a
     * program invokes <tt>{@link #exit exit}</tt> 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.
     *
     * <p> Uncaught exceptions are handled in shutdown hooks just as in any
     * other thread, by invoking the <tt>{@link ThreadGroup#uncaughtException
     * uncaughtException}</tt> method of the thread's <tt>{@link
     * ThreadGroup}</tt> object.  The default implementation of this method
     * prints the exception's stack trace to <tt>{@link System#err}</tt> and
     * terminates the thread; it does not cause the virtual machine to exit or
     * halt.
     *
     * <p> In rare circumstances the virtual machine may <i>abort</i>, that is,
     * stop running without shutting down cleanly.  This occurs when the
     * virtual machine is terminated externally, for example with the
     * <tt>SIGKILL</tt> signal on Unix or the <tt>TerminateProcess</tt> 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. <p>
     *
     * @param   hook
     *          An initialized but unstarted <tt>{@link Thread}</tt> 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
     *
     * @throws  IllegalStateException
     *          If the virtual machine is already in the process
     *          of shutting down
     *
     * @throws  SecurityException
     *          If a security manager is present and it denies
     *          <tt>{@link RuntimePermission}("shutdownHooks")</tt>
     *
     * @see #removeShutdownHook
     * @see #halt(int)
     * @see #exit(int)
     * @since 1.3
     */
    public void addShutdownHook(Thread hook) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("shutdownHooks"));
        }
        ApplicationShutdownHooks.add(hook);
    }

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


Params:
  • hook – the hook to remove
Throws:
See Also:
Returns:true if the specified hook had previously been
registered and was successfully de-registered, false
otherwise.
Since:1.3
/**
     * De-registers a previously-registered virtual-machine shutdown hook. <p>
     *
     * @param hook the hook to remove
     * @return <tt>true</tt> if the specified hook had previously been
     * registered and was successfully de-registered, <tt>false</tt>
     * otherwise.
     *
     * @throws  IllegalStateException
     *          If the virtual machine is already in the process of shutting
     *          down
     *
     * @throws  SecurityException
     *          If a security manager is present and it denies
     *          <tt>{@link RuntimePermission}("shutdownHooks")</tt>
     *
     * @see #addShutdownHook
     * @see #exit(int)
     * @since 1.3
     */
    public boolean removeShutdownHook(Thread hook) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("shutdownHooks"));
        }
        return ApplicationShutdownHooks.remove(hook);
    }

    
Forcibly terminates the currently running Java virtual machine.  This
method never returns normally.

 This method should be used with extreme caution.  Unlike the
exit method, this method does not cause shutdown
hooks to be started and does not run uninvoked finalizers if
finalization-on-exit has been enabled.  If the shutdown sequence has
already been initiated then this method does not wait for any running
shutdown hooks or finalizers to finish their work. 


Params:
  • status – 
        Termination status.  By convention, a nonzero status code
        indicates abnormal termination.  If the 
        exit (equivalently, 
        System.exit) method has already been invoked then this
        status code will override the status code passed to that method.
Throws:
See Also:
Since:1.3
/**
     * Forcibly terminates the currently running Java virtual machine.  This
     * method never returns normally.
     *
     * <p> This method should be used with extreme caution.  Unlike the
     * <tt>{@link #exit exit}</tt> method, this method does not cause shutdown
     * hooks to be started and does not run uninvoked finalizers if
     * finalization-on-exit has been enabled.  If the shutdown sequence has
     * already been initiated then this method does not wait for any running
     * shutdown hooks or finalizers to finish their work. <p>
     *
     * @param  status
     *         Termination status.  By convention, a nonzero status code
     *         indicates abnormal termination.  If the <tt>{@link Runtime#exit
     *         exit}</tt> (equivalently, <tt>{@link System#exit(int)
     *         System.exit}</tt>) method has already been invoked then this
     *         status code will override the status code passed to that method.
     *
     * @throws SecurityException
     *         If a security manager is present and its <tt>{@link
     *         SecurityManager#checkExit checkExit}</tt> method does not permit
     *         an exit with the specified status
     *
     * @see #exit
     * @see #addShutdownHook
     * @see #removeShutdownHook
     * @since 1.3
     */
    public void halt(int status) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkExit(status);
        }
        Shutdown.halt(status);
    }

    
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.
By default, finalization on exit is disabled.

If there is a security manager,
its checkExit method is first called
with 0 as its argument to ensure the exit is allowed.
This could result in a SecurityException.

Params:
  • value – true to enable finalization on exit, false to disable
Throws:
  • SecurityException – 
       if a security manager exists and its checkExit
       method doesn't allow the exit.
See Also:
Deprecated: This method is inherently unsafe.  It may result in
     finalizers being called on live objects while other threads are
     concurrently manipulating those objects, resulting in erratic
     behavior or deadlock.
Since:  JDK1.1
/**
     * 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.
     * By default, finalization on exit is disabled.
     *
     * <p>If there is a security manager,
     * its <code>checkExit</code> method is first called
     * with 0 as its argument to ensure the exit is allowed.
     * This could result in a SecurityException.
     *
     * @param value true to enable finalization on exit, false to disable
     * @deprecated  This method is inherently unsafe.  It may result in
     *      finalizers being called on live objects while other threads are
     *      concurrently manipulating those objects, resulting in erratic
     *      behavior or deadlock.
     *
     * @throws  SecurityException
     *        if a security manager exists and its <code>checkExit</code>
     *        method doesn't allow the exit.
     *
     * @see     java.lang.Runtime#exit(int)
     * @see     java.lang.Runtime#gc()
     * @see     java.lang.SecurityManager#checkExit(int)
     * @since   JDK1.1
     */
    @Deprecated
    public static void runFinalizersOnExit(boolean value) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            try {
                security.checkExit(0);
            } catch (SecurityException e) {
                throw new SecurityException("runFinalizersOnExit");
            }
        }
        Shutdown.setRunFinalizersOnExit(value);
    }

    
Executes the specified string command in a separate process.

This is a convenience method.  An invocation of the form
exec(command)
behaves in exactly the same way as the invocation
exec(command, null, null).

Params:
  • command –   a specified system command.
Throws:
See Also:
Returns: A new Process object for managing the subprocess
/**
     * Executes the specified string command in a separate process.
     *
     * <p>This is a convenience method.  An invocation of the form
     * <tt>exec(command)</tt>
     * behaves in exactly the same way as the invocation
     * <tt>{@link #exec(String, String[], File) exec}(command, null, null)</tt>.
     *
     * @param   command   a specified system command.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>command</code> is <code>null</code>
     *
     * @throws  IllegalArgumentException
     *          If <code>command</code> is empty
     *
     * @see     #exec(String[], String[], File)
     * @see     ProcessBuilder
     */
    public Process exec(String command) throws IOException {
        return exec(command, null, null);
    }

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

This is a convenience method.  An invocation of the form
exec(command, envp)
behaves in exactly the same way as the invocation
exec(command, envp, null).

Params:
  • command –   a specified system command.
  • 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.
Throws:
See Also:
Returns: A new Process object for managing the subprocess
/**
     * Executes the specified string command in a separate process with the
     * specified environment.
     *
     * <p>This is a convenience method.  An invocation of the form
     * <tt>exec(command, envp)</tt>
     * behaves in exactly the same way as the invocation
     * <tt>{@link #exec(String, String[], File) exec}(command, envp, null)</tt>.
     *
     * @param   command   a specified system command.
     *
     * @param   envp      array of strings, each element of which
     *                    has environment variable settings in the format
     *                    <i>name</i>=<i>value</i>, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the environment of the current process.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>command</code> is <code>null</code>,
     *          or one of the elements of <code>envp</code> is <code>null</code>
     *
     * @throws  IllegalArgumentException
     *          If <code>command</code> is empty
     *
     * @see     #exec(String[], String[], File)
     * @see     ProcessBuilder
     */
    public Process exec(String command, String[] envp) throws IOException {
        return exec(command, envp, null);
    }

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

This is a convenience method.  An invocation of the form
exec(command, envp, dir)
behaves in exactly the same way as the invocation
exec(cmdarray, envp, dir),
where cmdarray is an array of all the tokens in
command.

More precisely, the command string is broken into tokens using a StringTokenizer created by the call new StringTokenizer(command) with no
further modification of the character categories.  The tokens
produced by the tokenizer are then placed in the new string
array cmdarray, in the same order.

Params:
  • command –   a specified system command.
  • 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:
See Also:
Returns: A new Process object for managing the subprocess
Since:1.3
/**
     * Executes the specified string command in a separate process with the
     * specified environment and working directory.
     *
     * <p>This is a convenience method.  An invocation of the form
     * <tt>exec(command, envp, dir)</tt>
     * behaves in exactly the same way as the invocation
     * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, envp, dir)</tt>,
     * where <code>cmdarray</code> is an array of all the tokens in
     * <code>command</code>.
     *
     * <p>More precisely, the <code>command</code> string is broken
     * into tokens using a {@link StringTokenizer} created by the call
     * <code>new {@link StringTokenizer}(command)</code> with no
     * further modification of the character categories.  The tokens
     * produced by the tokenizer are then placed in the new string
     * array <code>cmdarray</code>, in the same order.
     *
     * @param   command   a specified system command.
     *
     * @param   envp      array of strings, each element of which
     *                    has environment variable settings in the format
     *                    <i>name</i>=<i>value</i>, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the environment of the current process.
     *
     * @param   dir       the working directory of the subprocess, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the working directory of the current process.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>command</code> is <code>null</code>,
     *          or one of the elements of <code>envp</code> is <code>null</code>
     *
     * @throws  IllegalArgumentException
     *          If <code>command</code> is empty
     *
     * @see     ProcessBuilder
     * @since 1.3
     */
    public Process exec(String command, String[] envp, File dir)
        throws IOException {
        if (command.length() == 0)
            throw new IllegalArgumentException("Empty command");

        StringTokenizer st = new StringTokenizer(command);
        String[] cmdarray = new String[st.countTokens()];
        for (int i = 0; st.hasMoreTokens(); i++)
            cmdarray[i] = st.nextToken();
        return exec(cmdarray, envp, dir);
    }

    
Executes the specified command and arguments in a separate process.

This is a convenience method.  An invocation of the form
exec(cmdarray)
behaves in exactly the same way as the invocation
exec(cmdarray, null, null).

Params:
  • cmdarray –  array containing the command to call and
                   its arguments.
Throws:
See Also:
Returns: A new Process object for managing the subprocess
/**
     * Executes the specified command and arguments in a separate process.
     *
     * <p>This is a convenience method.  An invocation of the form
     * <tt>exec(cmdarray)</tt>
     * behaves in exactly the same way as the invocation
     * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, null, null)</tt>.
     *
     * @param   cmdarray  array containing the command to call and
     *                    its arguments.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>cmdarray</code> is <code>null</code>,
     *          or one of the elements of <code>cmdarray</code> is <code>null</code>
     *
     * @throws  IndexOutOfBoundsException
     *          If <code>cmdarray</code> is an empty array
     *          (has length <code>0</code>)
     *
     * @see     ProcessBuilder
     */
    public Process exec(String cmdarray[]) throws IOException {
        return exec(cmdarray, null, null);
    }

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

This is a convenience method.  An invocation of the form
exec(cmdarray, envp)
behaves in exactly the same way as the invocation
exec(cmdarray, envp, null).

Params:
  • 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.
Throws:
See Also:
Returns: A new Process object for managing the subprocess
/**
     * Executes the specified command and arguments in a separate process
     * with the specified environment.
     *
     * <p>This is a convenience method.  An invocation of the form
     * <tt>exec(cmdarray, envp)</tt>
     * behaves in exactly the same way as the invocation
     * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, envp, null)</tt>.
     *
     * @param   cmdarray  array containing the command to call and
     *                    its arguments.
     *
     * @param   envp      array of strings, each element of which
     *                    has environment variable settings in the format
     *                    <i>name</i>=<i>value</i>, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the environment of the current process.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>cmdarray</code> is <code>null</code>,
     *          or one of the elements of <code>cmdarray</code> is <code>null</code>,
     *          or one of the elements of <code>envp</code> is <code>null</code>
     *
     * @throws  IndexOutOfBoundsException
     *          If <code>cmdarray</code> is an empty array
     *          (has length <code>0</code>)
     *
     * @see     ProcessBuilder
     */
    public Process exec(String[] cmdarray, String[] envp) throws IOException {
        return exec(cmdarray, envp, null);
    }


    
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. 
Params:
  • 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:
See Also:
Returns: A new Process object for managing the subprocess
Since:1.3
/**
     * Executes the specified command and arguments in a separate process with
     * the specified environment and working directory.
     *
     * <p>Given an array of strings <code>cmdarray</code>, representing the
     * tokens of a command line, and an array of strings <code>envp</code>,
     * representing "environment" variable settings, this method creates
     * a new process in which to execute the specified command.
     *
     * <p>This method checks that <code>cmdarray</code> 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.
     *
     * <p>If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the
     * environment settings of the current process.
     *
     * <p>{@link ProcessBuilder#start()} is now the preferred way to
     * start a process with a modified environment.
     *
     * <p>The working directory of the new subprocess is specified by <tt>dir</tt>.
     * If <tt>dir</tt> is <tt>null</tt>, the subprocess inherits the
     * current working directory of the current process.
     *
     * <p>If a security manager exists, its
     * {@link SecurityManager#checkExec checkExec}
     * method is invoked with the first component of the array
     * <code>cmdarray</code> as its argument. This may result in a
     * {@link SecurityException} being thrown.
     *
     * <p>Starting an operating system process is highly system-dependent.
     * Among the many things that can go wrong are:
     * <ul>
     * <li>The operating system program file was not found.
     * <li>Access to the program file was denied.
     * <li>The working directory does not exist.
     * </ul>
     *
     * <p>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 {@link IOException}.
     *
     *
     * @param   cmdarray  array containing the command to call and
     *                    its arguments.
     *
     * @param   envp      array of strings, each element of which
     *                    has environment variable settings in the format
     *                    <i>name</i>=<i>value</i>, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the environment of the current process.
     *
     * @param   dir       the working directory of the subprocess, or
     *                    <tt>null</tt> if the subprocess should inherit
     *                    the working directory of the current process.
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @throws  NullPointerException
     *          If <code>cmdarray</code> is <code>null</code>,
     *          or one of the elements of <code>cmdarray</code> is <code>null</code>,
     *          or one of the elements of <code>envp</code> is <code>null</code>
     *
     * @throws  IndexOutOfBoundsException
     *          If <code>cmdarray</code> is an empty array
     *          (has length <code>0</code>)
     *
     * @see     ProcessBuilder
     * @since 1.3
     */
    public Process exec(String[] cmdarray, String[] envp, File dir)
        throws IOException {
        return new ProcessBuilder(cmdarray)
            .environment(envp)
            .directory(dir)
            .start();
    }

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

 This value may change during a particular invocation of the virtual
machine.  Applications that are sensitive to the number of available
processors should therefore occasionally poll this property and adjust
their resource usage appropriately. 


Returns: the maximum number of processors available to the virtual
         machine; never smaller than one
Since:1.4
/**
     * Returns the number of processors available to the Java virtual machine.
     *
     * <p> This value may change during a particular invocation of the virtual
     * machine.  Applications that are sensitive to the number of available
     * processors should therefore occasionally poll this property and adjust
     * their resource usage appropriately. </p>
     *
     * @return  the maximum number of processors available to the virtual
     *          machine; never smaller than one
     * @since 1.4
     */
    public native int availableProcessors();

    
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.
/**
     * Returns the amount of free memory in the Java Virtual Machine.
     * Calling the
     * <code>gc</code> method may result in increasing the value returned
     * by <code>freeMemory.</code>
     *
     * @return  an approximation to the total amount of memory currently
     *          available for future allocated objects, measured in bytes.
     */
    public native long freeMemory();

    
Returns the total amount of memory in the Java virtual machine.
The value returned by this method may vary over time, depending on
the host environment.


Note that the amount of memory required to hold an object of any
given type may be implementation-dependent.

Returns: the total amount of memory currently available for current
         and future objects, measured in bytes.
/**
     * Returns the total amount of memory in the Java virtual machine.
     * The value returned by this method may vary over time, depending on
     * the host environment.
     * <p>
     * Note that the amount of memory required to hold an object of any
     * given type may be implementation-dependent.
     *
     * @return  the total amount of memory currently available for current
     *          and future objects, measured in bytes.
     */
    public native long totalMemory();

    
Returns the maximum amount of memory that the Java virtual machine will attempt to use. If there is no inherent limit then the value Long.MAX_VALUE will be returned. 


Returns: the maximum amount of memory that the virtual machine will
         attempt to use, measured in bytes
Since:1.4
/**
     * Returns the maximum amount of memory that the Java virtual machine will
     * attempt to use.  If there is no inherent limit then the value {@link
     * java.lang.Long#MAX_VALUE} will be returned. </p>
     *
     * @return  the maximum amount of memory that the virtual machine will
     *          attempt to use, measured in bytes
     * @since 1.4
     */
    public native long maxMemory();

    
Runs the garbage collector.
Calling this method suggests that the Java virtual machine expend
effort toward recycling unused objects in order to make the memory
they currently occupy available for quick reuse. When control
returns from the method call, the virtual machine has made
its best effort to recycle all discarded objects.


The name gc stands for "garbage
collector". The virtual machine performs this recycling
process automatically as needed, in a separate thread, even if the
gc method is not invoked explicitly.

 The method System.gc() is the conventional and convenient means of invoking this method. 
/**
     * Runs the garbage collector.
     * Calling this method suggests that the Java virtual machine expend
     * effort toward recycling unused objects in order to make the memory
     * they currently occupy available for quick reuse. When control
     * returns from the method call, the virtual machine has made
     * its best effort to recycle all discarded objects.
     * <p>
     * The name <code>gc</code> stands for "garbage
     * collector". The virtual machine performs this recycling
     * process automatically as needed, in a separate thread, even if the
     * <code>gc</code> method is not invoked explicitly.
     * <p>
     * The method {@link System#gc()} is the conventional and convenient
     * means of invoking this method.
     */
    public native void gc();

    /* Wormhole for calling java.lang.ref.Finalizer.runFinalization */
    private static native void runFinalization0();

    
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:
/**
     * Runs the finalization methods of any objects pending finalization.
     * Calling this method suggests that the Java virtual machine expend
     * effort toward running the <code>finalize</code> methods of objects
     * that have been found to be discarded but whose <code>finalize</code>
     * 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.
     * <p>
     * The virtual machine performs the finalization process
     * automatically as needed, in a separate thread, if the
     * <code>runFinalization</code> method is not invoked explicitly.
     * <p>
     * The method {@link System#runFinalization()} is the conventional
     * and convenient means of invoking this method.
     *
     * @see     java.lang.Object#finalize()
     */
    public void runFinalization() {
        runFinalization0();
    }

    
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.

Params:
  • on –   true to enable instruction tracing;
              false to disable this feature.
/**
     * Enables/Disables tracing of instructions.
     * If the <code>boolean</code> argument is <code>true</code>, 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.
     * <p>
     * If the <code>boolean</code> argument is <code>false</code>, this
     * method causes the virtual machine to stop performing the
     * detailed instruction trace it is performing.
     *
     * @param   on   <code>true</code> to enable instruction tracing;
     *               <code>false</code> to disable this feature.
     */
    public native void traceInstructions(boolean on);

    
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.

Params:
  • on –   true to enable instruction tracing;
              false to disable this feature.
/**
     * Enables/Disables tracing of method calls.
     * If the <code>boolean</code> argument is <code>true</code>, 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.
     * <p>
     * Calling this method with argument false suggests that the
     * virtual machine cease emitting per-call debugging information.
     *
     * @param   on   <code>true</code> to enable instruction tracing;
     *               <code>false</code> to disable this feature.
     */
    public native void traceMethodCalls(boolean on);

    
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 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. 
Params:
  • filename –   the file to load.
Throws:
See Also:
/**
     * Loads the specified filename as a dynamic library. The filename
     * argument must be a complete path name,
     * (for example
     * <code>Runtime.getRuntime().load("/home/avh/lib/libX11.so");</code>).
     * <p>
     * First, if there is a security manager, its <code>checkLink</code>
     * method is called with the <code>filename</code> as its argument.
     * This may result in a security exception.
     * <p>
     * This is similar to the method {@link #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.
     * <p>
     * The method {@link System#load(String)} is the conventional and
     * convenient means of invoking this method.
     *
     * @param      filename   the file to load.
     * @exception  SecurityException  if a security manager exists and its
     *             <code>checkLink</code> method doesn't allow
     *             loading of the specified dynamic library
     * @exception  UnsatisfiedLinkError  if the file does not exist.
     * @exception  NullPointerException if <code>filename</code> is
     *             <code>null</code>
     * @see        java.lang.Runtime#getRuntime()
     * @see        java.lang.SecurityException
     * @see        java.lang.SecurityManager#checkLink(java.lang.String)
     */
    @CallerSensitive
    public void load(String filename) {
        load0(Reflection.getCallerClass(), filename);
    }

    synchronized void load0(Class fromClass, String filename) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkLink(filename);
        }
        if (!(new File(filename).isAbsolute())) {
            throw new UnsatisfiedLinkError(
                "Expecting an absolute path of the library: " + filename);
        }
        ClassLoader.loadLibrary(fromClass, filename, true);
    }

    
Loads the dynamic library with the specified library name.
A file containing native code is loaded from the local file system
from a place where library files are conventionally obtained. The
details of this process are implementation-dependent. The
mapping from a library name to a specific filename is done in a
system-specific manner.


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

 The method System.loadLibrary(String) is the conventional and convenient means of invoking this method. If native methods are to be used in the implementation of a class, a standard strategy is to put the native code in a library file (call it LibFile) and then to put a static initializer:

static { System.loadLibrary("LibFile"); }


within the class declaration. When the class is loaded and
initialized, the necessary native code implementation for the native
methods will then be loaded as well.


If this method is called more than once with the same library
name, the second and subsequent calls are ignored.

Params:
  • libname –   the name of the library.
Throws:
See Also:
/**
     * Loads the dynamic library with the specified library name.
     * A file containing native code is loaded from the local file system
     * from a place where library files are conventionally obtained. The
     * details of this process are implementation-dependent. The
     * mapping from a library name to a specific filename is done in a
     * system-specific manner.
     * <p>
     * First, if there is a security manager, its <code>checkLink</code>
     * method is called with the <code>libname</code> as its argument.
     * This may result in a security exception.
     * <p>
     * The method {@link System#loadLibrary(String)} is the conventional
     * and convenient means of invoking this method. If native
     * methods are to be used in the implementation of a class, a standard
     * strategy is to put the native code in a library file (call it
     * <code>LibFile</code>) and then to put a static initializer:
     * <blockquote><pre>
     * static { System.loadLibrary("LibFile"); }
     * </pre></blockquote>
     * within the class declaration. When the class is loaded and
     * initialized, the necessary native code implementation for the native
     * methods will then be loaded as well.
     * <p>
     * If this method is called more than once with the same library
     * name, the second and subsequent calls are ignored.
     *
     * @param      libname   the name of the library.
     * @exception  SecurityException  if a security manager exists and its
     *             <code>checkLink</code> method doesn't allow
     *             loading of the specified dynamic library
     * @exception  UnsatisfiedLinkError  if the library does not exist.
     * @exception  NullPointerException if <code>libname</code> is
     *             <code>null</code>
     * @see        java.lang.SecurityException
     * @see        java.lang.SecurityManager#checkLink(java.lang.String)
     */
    @CallerSensitive
    public void loadLibrary(String libname) {
        loadLibrary0(Reflection.getCallerClass(), libname);
    }

    synchronized void loadLibrary0(Class fromClass, String libname) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkLink(libname);
        }
        if (libname.indexOf((int)File.separatorChar) != -1) {
            throw new UnsatisfiedLinkError(
    "Directory separator should not appear in library name: " + libname);
        }
        ClassLoader.loadLibrary(fromClass, libname, false);
    }

    
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.

Params:
  • in – InputStream to localize
See Also:
Returns:    a localized input stream
Deprecated:As of JDK 1.1, the preferred way to translate a byte
stream in the local encoding into a character stream in Unicode is via
the InputStreamReader and BufferedReader
classes.
/**
     * Creates a localized version of an input stream. This method takes
     * an <code>InputStream</code> and returns an <code>InputStream</code>
     * 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.
     * <p>
     * If the argument is already a localized stream, it may be returned
     * as the result.
     *
     * @param      in InputStream to localize
     * @return     a localized input stream
     * @see        java.io.InputStream
     * @see        java.io.BufferedReader#BufferedReader(java.io.Reader)
     * @see        java.io.InputStreamReader#InputStreamReader(java.io.InputStream)
     * @deprecated As of JDK&nbsp;1.1, the preferred way to translate a byte
     * stream in the local encoding into a character stream in Unicode is via
     * the <code>InputStreamReader</code> and <code>BufferedReader</code>
     * classes.
     */
    @Deprecated
    public InputStream getLocalizedInputStream(InputStream in) {
        return in;
    }

    
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.

Params:
  • out – OutputStream to localize
See Also:
Deprecated:As of JDK 1.1, the preferred way to translate a
Unicode character stream into a byte stream in the local encoding is via
the OutputStreamWriter, BufferedWriter, and
PrintWriter classes.
Returns:    a localized output stream
/**
     * Creates a localized version of an output stream. This method
     * takes an <code>OutputStream</code> and returns an
     * <code>OutputStream</code> 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.
     * <p>
     * If the argument is already a localized stream, it may be returned
     * as the result.
     *
     * @deprecated As of JDK&nbsp;1.1, the preferred way to translate a
     * Unicode character stream into a byte stream in the local encoding is via
     * the <code>OutputStreamWriter</code>, <code>BufferedWriter</code>, and
     * <code>PrintWriter</code> classes.
     *
     * @param      out OutputStream to localize
     * @return     a localized output stream
     * @see        java.io.OutputStream
     * @see        java.io.BufferedWriter#BufferedWriter(java.io.Writer)
     * @see        java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
     * @see        java.io.PrintWriter#PrintWriter(java.io.OutputStream)
     */
    @Deprecated
    public OutputStream getLocalizedOutputStream(OutputStream out) {
        return out;
    }

}