/* * 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; /** * 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 <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 */    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.     *     * <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.     *     * <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. <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.     *     * <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.     *     * <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.     *     * <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.     *     * <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.     *     * <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.     *     * <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.     *     * <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

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