/*
 * @(#)Runtime.java	1.67 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

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
 * @version 1.67, 01/23/03
 * @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.
     *
     * <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"));
	}
	Shutdown.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 Shutdown.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
     */
    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);
    }

    /* Helper for exec
     */
    private native Process execInternal(String cmdarray[], String envp[], String path) 
	 throws IOException;

    /**
     * Executes the specified string command in a separate process. 
     * <p>
     * The <code>command</code> argument is parsed into tokens and then 
     * executed as a command in a separate process. The token parsing is 
     * done by a {@link java.util.StringTokenizer} created by the call:
     * <blockquote><pre>
     * new StringTokenizer(command)
     * </pre></blockquote> 
     * with no further modifications of the character categories. 
     * This method has exactly the same effect as 
     * <code>exec(command, null)</code>. 
     *
     * @param      command   a specified system command.
     * @return     a <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a subprocess.
     * @exception  IOException if an I/O error occurs
     * @exception  NullPointerException if <code>command</code> is 
     *             <code>null</code>
     * @exception  IllegalArgumentException if <code>command</code> is empty 
     *             
     * @see        java.lang.Runtime#exec(java.lang.String, java.lang.String[])
     * @see     java.lang.SecurityManager#checkExec(java.lang.String)
     */
    public Process exec(String command) throws IOException {
	return exec(command, null);
    }

    /**
     * Executes the specified string command in a separate process with the 
     * specified environment. 
     * <p>
     * This method breaks the <code>command</code> string into tokens and 
     * creates a new array <code>cmdarray</code> containing the tokens in the 
     * order that they were produced by the string tokenizer; it 
     * then performs the call <code>exec(cmdarray, envp)</code>. The token
     * parsing is done by a {@link java.util.StringTokenizer} created by 
     * the call: 
     * <blockquote><pre>
     * new StringTokenizer(command)
     * </pre></blockquote>
     * with no further modification of the character categories. 
     *
     * <p>
     * The environment variable settings are specified by <tt>envp</tt>.
     * If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the 
     * environment settings of the current process.
     *
     * @param      cmd       a specified system command.
     * @param      envp      array of strings, each element of which 
     *                       has environment variable settings in format
     *                       <i>name</i>=<i>value</i>.
     * @return     a <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a subprocess.
     * @exception  IOException if an I/O error occurs
     * @exception  NullPointerException if <code>cmd</code> is null
     * @exception  IllegalArgumentException if <code>cmd</code> is empty
     * @see        java.lang.Runtime#exec(java.lang.String[])
     * @see        java.lang.Runtime#exec(java.lang.String[], java.lang.String[])
     * @see        java.lang.SecurityManager#checkExec(java.lang.String)
     */
    public Process exec(String cmd, String envp[]) throws IOException {
        return exec(cmd, envp, null);
    }
    
    /**
     * Executes the specified string command in a separate process with the
     * specified environment and working directory. 
     * <p>
     * This method breaks the <code>command</code> string into tokens and 
     * creates a new array <code>cmdarray</code> containing the tokens in the 
     * order that they were produced by the string tokenizer; it 
     * then performs the call <code>exec(cmdarray, envp)</code>. The token
     * parsing is done by a {@link java.util.StringTokenizer} created by 
     * the call: 
     * <blockquote><pre>
     * new StringTokenizer(command)
     * </pre></blockquote>
     * with no further modification of the character categories. 
     *
     * <p>
     * The environment variable settings are specified by <tt>envp</tt>.
     * If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the 
     * environment settings of the current process.
     *
     * <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.
     *
     * @param      command   a specified system command.
     * @param      envp      array of strings, each element of which 
     *                       has environment variable settings in format
     *                       <i>name</i>=<i>value</i>.
     * @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 <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a subprocess.
     * @exception  IOException if an I/O error occurs
     * @exception  NullPointerException if <code>command</code> is 
     *             <code>null</code>
     * @exception  IllegalArgumentException if <code>command</code> is empty
     * @see        java.lang.Runtime#exec(java.lang.String[], java.lang.String[], File)
     * @see        java.lang.SecurityManager#checkExec(java.lang.String)
     * @since 1.3
     */
    public Process exec(String command, String envp[], File dir) 
        throws IOException {
	int count = 0;
	String cmdarray[];
 	StringTokenizer st;

        if (command.length() == 0)
            throw new IllegalArgumentException("Empty command"); 

	st = new StringTokenizer(command);
 	count = st.countTokens();

	cmdarray = new String[count];
	st = new StringTokenizer(command);
	count = 0;
 	while (st.hasMoreTokens()) {
 		cmdarray[count++] = st.nextToken();
 	}
	return exec(cmdarray, envp, dir);
    }

    /**
     * Executes the specified command and arguments in a separate process.
     * <p>
     * The command specified by the tokens in <code>cmdarray</code> is 
     * executed as a command in a separate process. This has exactly the 
     * same effect as <code>exec(cmdarray, null)</code>. 
     * <p>
     * If there is a security manager, its <code>checkExec</code> 
     * method is called with the first component of the array 
     * <code>cmdarray</code> as its argument. This may result in a security 
     * exception. 
     *
     * @param      cmdarray   array containing the command to call and
     *                        its arguments.
     * @return     a <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a subprocess.
     * @exception  IOException if an I/O error occurs
     * @exception  NullPointerException if <code>cmdarray</code> is 
     *             <code>null</code>
     * @exception  IndexOutOfBoundsException if <code>cmdarray</code> is an
     *             empty array (has length <code>0</code>).
     * @see        java.lang.Runtime#exec(java.lang.String[], java.lang.String[])
     * @see        java.lang.SecurityManager#checkExec(java.lang.String)
     */
    public Process exec(String cmdarray[]) throws IOException {
	return exec(cmdarray, null);
    }

    /**
     * Executes the specified command and arguments in a separate process
     * with the specified environment. 
     * <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>
     * If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the 
     * environment settings of the current process.
     *
     * @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 format
     *                        <i>name</i>=<i>value</i>.
     * @return     a <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a subprocess.
     * @exception  IOException if an I/O error occurs
     * @exception  NullPointerException if <code>cmdarray</code> is 
     *             <code>null</code>
     * @exception  IndexOutOfBoundsException if <code>cmdarray</code> is an
     *             empty array (has length <code>0</code>).
     * @see     java.lang.Process
     * @see     java.lang.SecurityException
     * @see     java.lang.SecurityManager#checkExec(java.lang.String)
     */
    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. 
     * <p>
     * If there is a security manager, its <code>checkExec</code> 
     * method is called with the first component of the array 
     * <code>cmdarray</code> as its argument. This may result in a security 
     * exception. 
     * <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>
     * If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the 
     * environment settings of the current process.
     *
     * <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.
     *
     *
     * @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 format
     *                        <i>name</i>=<i>value</i>.
     * @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 <code>Process</code> object for managing the subprocess.
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkExec</code> method doesn't allow creation of a 
     *             subprocess.
     * @exception  NullPointerException if <code>cmdarray</code> is 
     *             <code>null</code>
     * @exception  IndexOutOfBoundsException if <code>cmdarray</code> is an
     *             empty array (has length <code>0</code>).
     * @exception  IOException if an I/O error occurs.
     * @see     java.lang.Process
     * @see     java.lang.SecurityException
     * @see     java.lang.SecurityManager#checkExec(java.lang.String)
     * @since 1.3
     */
    public Process exec(String cmdarray[], String envp[], File dir) 
	throws IOException {	
	cmdarray = (String[])cmdarray.clone();
	envp = (envp != null ? (String[])envp.clone() : null);

        if (cmdarray.length == 0) {
            throw new IndexOutOfBoundsException();            
        }
        for (int i = 0; i < cmdarray.length; i++) {
            if (cmdarray[i] == null) {
                throw new NullPointerException();
            }
        }
        if (envp != null) {
            for (int i = 0; i < envp.length; i++) {
                if (envp[i] == null) {
                    throw new NullPointerException();
                }
            }
        }
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkExec(cmdarray[0]);
	}
        String path = (dir == null ? null : dir.getPath());
	return execInternal(cmdarray, envp, path);
    }

    /**
     * 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
     */
    public native int availableProcessors();

    /**
     * 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.
     * <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 {@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
     */
    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. 
     * <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 <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 <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 <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. 
     * From <code>java_g</code> it will automagically insert "_g" before the
     * ".so" (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.
     * @see        java.lang.Runtime#getRuntime()
     * @see        java.lang.SecurityException
     * @see        java.lang.SecurityManager#checkLink(java.lang.String)
     */
    public void load(String filename) {
        load0(System.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. 
     * <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.
     * @see        java.lang.SecurityException
     * @see        java.lang.SecurityManager#checkLink(java.lang.String)
     */
    public void loadLibrary(String libname) {
        loadLibrary0(System.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 <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 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.
     */
    public InputStream getLocalizedInputStream(InputStream in) {
	return in;
    }

    /**
     * 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 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)
     */
    public OutputStream getLocalizedOutputStream(OutputStream out) {
	return out;
    }

}