/*

 * Copyright (c) 1995, 2021, Oracle and/or its affiliates. All rights reserved.

 * Copyright (c) 2019, Azul Systems, Inc. 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.math.BigInteger;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import java.util.stream.Collectors;

import java.util.List;

import java.util.Optional;

import java.util.StringTokenizer;

import jdk.internal.access.SharedSecrets;

import jdk.internal.loader.NativeLibrary;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.Reflection;

/**

 * Every Java application has a single instance of class

 * {@code Runtime} 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} method.

 * <p>

 * An application cannot create its own instance of this class.

 *

 * @see     java.lang.Runtime#getRuntime()

 * @since   1.0

 */

public class Runtime {

    private static final Runtime currentRuntime = new Runtime();

    private static Version version;

    /**

     * Returns the runtime object associated with the current Java application.

     * Most of the methods of class {@code Runtime} are instance

     * methods and must be invoked with respect to the current runtime object.

     *

     * @return  the {@code Runtime} 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> All registered {@linkplain #addShutdownHook shutdown hooks}, if any,

     * are started in some unspecified order and allowed to run concurrently

     * until they finish.  Once this is done the virtual machine

     * {@linkplain #halt halts}.

     *

     * <p> If this method is invoked after all shutdown hooks have already

     * been run and the status is nonzero then this method halts the

     * virtual machine with the given status code. Otherwise, this method

     * blocks indefinitely.

     *

     * <p> The {@link System#exit(int) System.exit} method is the

     * conventional and convenient means of invoking this method.

     *

     * @param  status

     *         Termination status.  By convention, a nonzero status code

     *         indicates abnormal termination.

     *

     * @throws SecurityException

     *         If a security manager is present and its

     *         {@link SecurityManager#checkExit checkExit} method does not permit

     *         exiting with the specified status

     *

     * @see java.lang.SecurityException

     * @see java.lang.SecurityManager#checkExit(int)

     * @see #addShutdownHook

     * @see #removeShutdownHook

     * @see #halt(int)

     */

    public void exit(int status) {

        @SuppressWarnings("removal")

        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>

     *

     *   <li> The program <i>exits</i> normally, when the last non-daemon

     *   thread exits or when the {@link #exit exit} (equivalently,

     *   {@link System#exit(int) System.exit}) method is invoked, or

     *

     *   <li> The virtual machine is <i>terminated</i> in response to a

     *   user interrupt, such as typing {@code ^C}, 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

     * 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 {@link #exit exit} method.

     *

     * <p> Once the shutdown sequence has begun it can be stopped only by

     * invoking the {@link #halt halt} 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

     * {@link IllegalStateException} 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 {@link #exit 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.

     *

     * <p> Uncaught exceptions are handled in shutdown hooks just as in any

     * other thread, by invoking the

     * {@link ThreadGroup#uncaughtException uncaughtException} method of the

     * thread's {@link ThreadGroup} object. The default implementation of this

     * method prints the exception's stack trace to {@link System#err} 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

     * {@code SIGKILL} signal on Unix or the {@code 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.

     *

     * @param   hook

     *          An initialized but unstarted {@link Thread} object

     *

     * @throws  IllegalArgumentException

     *          If the specified hook has already been registered,

     *          or if it can be determined that the hook is already running or

     *          has already been run

     *

     * @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

     *          {@link RuntimePermission}{@code ("shutdownHooks")}

     *

     * @see #removeShutdownHook

     * @see #halt(int)

     * @see #exit(int)

     * @since 1.3

     */

    public void addShutdownHook(Thread hook) {

        @SuppressWarnings("removal")

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(new RuntimePermission("shutdownHooks"));

        }

        ApplicationShutdownHooks.add(hook);

    }

    /**

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

     *

     * @param hook the hook to remove

     * @return {@code true} if the specified hook had previously been

     * registered and was successfully de-registered, {@code false}

     * 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

     *          {@link RuntimePermission}{@code ("shutdownHooks")}

     *

     * @see #addShutdownHook

     * @see #exit(int)

     * @since 1.3

     */

    public boolean removeShutdownHook(Thread hook) {

        @SuppressWarnings("removal")

        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

     * {@link #exit exit} method, this method does not cause shutdown

     * hooks to be started.  If the shutdown sequence has already been

     * initiated then this method does not wait for any running

     * shutdown hooks to finish their work.

     *

     * @param  status

     *         Termination status. By convention, a nonzero status code

     *         indicates abnormal termination. If the {@link Runtime#exit exit}

     *         (equivalently, {@link System#exit(int) System.exit}) 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

     *         {@link SecurityManager#checkExit checkExit} method

     *         does not permit an exit with the specified status

     *

     * @see #exit

     * @see #addShutdownHook

     * @see #removeShutdownHook

     * @since 1.3

     */

    public void halt(int status) {

        @SuppressWarnings("removal")

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkExit(status);

        }

        Shutdown.beforeHalt();

        Shutdown.halt(status);

    }

    /**

     * Executes the specified string command in a separate process.

     *

     * <p>This is a convenience method.  An invocation of the form

     * {@code exec(command)}

     * behaves in exactly the same way as the invocation

     * {@link #exec(String, String[], File) exec}{@code (command, null, null)}.

     *

     * @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} is {@code null}

     *

     * @throws  IllegalArgumentException

     *          If {@code command} 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

     * {@code exec(command, envp)}

     * behaves in exactly the same way as the invocation

     * {@link #exec(String, String[], File) exec}{@code (command, envp, null)}.

     *

     * @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

     *                    {@code null} 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} is {@code null},

     *          or one of the elements of {@code envp} is {@code null}

     *

     * @throws  IllegalArgumentException

     *          If {@code command} 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

     * {@code exec(command, envp, dir)}

     * behaves in exactly the same way as the invocation

     * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, dir)},

     * where {@code cmdarray} is an array of all the tokens in

     * {@code command}.

     *

     * <p>More precisely, the {@code command} string is broken

     * into tokens using a {@link StringTokenizer} created by the call

     * {@code 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 {@code cmdarray}, 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

     *                    {@code null} if the subprocess should inherit

     *                    the environment of the current process.

     *

     * @param   dir       the working directory of the subprocess, or

     *                    {@code null} 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} is {@code null},

     *          or one of the elements of {@code envp} is {@code null}

     *

     * @throws  IllegalArgumentException

     *          If {@code command} is empty

     *

     * @see     ProcessBuilder

     * @since 1.3

     */

    public Process exec(String command, String[] envp, File dir)

        throws IOException {

        if (command.isEmpty())

            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

     * {@code exec(cmdarray)}

     * behaves in exactly the same way as the invocation

     * {@link #exec(String[], String[], File) exec}{@code (cmdarray, null, null)}.

     *

     * @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} is {@code null},

     *          or one of the elements of {@code cmdarray} is {@code null}

     *

     * @throws  IndexOutOfBoundsException

     *          If {@code cmdarray} is an empty array

     *          (has length {@code 0})

     *

     * @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

     * {@code exec(cmdarray, envp)}

     * behaves in exactly the same way as the invocation

     * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, null)}.

     *

     * @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

     *                    {@code null} 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} is {@code null},

     *          or one of the elements of {@code cmdarray} is {@code null},

     *          or one of the elements of {@code envp} is {@code null}

     *

     * @throws  IndexOutOfBoundsException

     *          If {@code cmdarray} is an empty array

     *          (has length {@code 0})

     *

     * @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.

     *

     * <p>Given an array of strings {@code cmdarray}, representing the

     * tokens of a command line, and an array of strings {@code envp},

     * representing "environment" variable settings, this method creates

     * a new process in which to execute the specified command.

     *

     * <p>This method checks that {@code 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.

     *

     * <p>If {@code envp} is {@code null}, the subprocess inherits the

     * environment settings of the current process.

     *

     * <p>A minimal set of system dependent environment variables may

     * be required to start a process on some operating systems.

     * As a result, the subprocess may inherit additional environment variable

     * settings beyond those in the specified environment.

     *

     * <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 {@code dir}.

     * If {@code dir} is {@code null}, 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} 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}.

     *

     * <p>If the operating system does not support the creation of

     * processes, an {@link UnsupportedOperationException} will be thrown.

     *

     *

     * @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

     *                    {@code null} if the subprocess should inherit

     *                    the environment of the current process.

     *

     * @param   dir       the working directory of the subprocess, or

     *                    {@code null} 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  UnsupportedOperationException

     *          If the operating system does not support the creation of processes.

     *

     * @throws  IOException

     *          If an I/O error occurs

     *

     * @throws  NullPointerException

     *          If {@code cmdarray} is {@code null},

     *          or one of the elements of {@code cmdarray} is {@code null},

     *          or one of the elements of {@code envp} is {@code null}

     *

     * @throws  IndexOutOfBoundsException

     *          If {@code cmdarray} is an empty array

     *          (has length {@code 0})

     *

     * @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.

     *

     * <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

     * {@code gc} method may result in increasing the value returned

     * by {@code freeMemory.}

     *

     * @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.

     *

     * @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 in the Java Virtual Machine.

     * <p>

     * 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 reuse

     * by the Java Virtual Machine.

     * When control returns from the method call, the Java Virtual Machine

     * has made a best effort to reclaim space from all unused objects.

     * There is no guarantee that this effort will recycle any particular

     * number of unused objects, reclaim any particular amount of space, or

     * complete at any particular time, if at all, before the method returns or ever.

     * There is also no guarantee that this effort will determine

     * the change of reachability in any particular number of objects,

     * or that any particular number of {@link java.lang.ref.Reference Reference}

     * objects will be cleared and enqueued.

     * <p>

     * The name {@code gc} stands for "garbage

     * collector". The Java Virtual Machine performs this recycling

     * process automatically as needed, in a separate thread, even if the

     * {@code gc} 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();

    /**

     * 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} methods of objects

     * that have been found to be discarded but whose {@code 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.

     * <p>

     * The virtual machine performs the finalization process

     * automatically as needed, in a separate thread, if the

     * {@code runFinalization} 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() {

        SharedSecrets.getJavaLangRefAccess().runFinalization();

    }

    /**

     * Loads the native library specified by the filename argument.  The filename

     * argument must be an absolute path name.

     * (for example

     * {@code Runtime.getRuntime().load("/home/avh/lib/libX11.so");}).

     *

     * If the filename argument, when stripped of any platform-specific library

     * prefix, path, and file extension, indicates a library whose name is,

     * for example, L, and a native library called L is statically linked

     * with the VM, then the JNI_OnLoad_L function exported by the library

     * is invoked rather than attempting to load a dynamic library.

     * A filename matching the argument does not have to exist in the file

     * system.

     * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>

     * for more details.

     *

     * Otherwise, the filename argument is mapped to a native library image in

     * an implementation-dependent manner.

     * <p>

     * First, if there is a security manager, its {@code checkLink}

     * method is called with the {@code filename} 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.

     * @throws     SecurityException  if a security manager exists and its

     *             {@code checkLink} method doesn't allow

     *             loading of the specified dynamic library

     * @throws     UnsatisfiedLinkError  if either the filename is not an

     *             absolute path name, the native library is not statically

     *             linked with the VM, or the library cannot be mapped to

     *             a native library image by the host system.

     * @throws     NullPointerException if {@code filename} is

     *             {@code null}

     * @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);

    }

    void load0(Class<?> fromClass, String filename) {

        @SuppressWarnings("removal")

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            security.checkLink(filename);

        }

        File file = new File(filename);

        if (!file.isAbsolute()) {

            throw new UnsatisfiedLinkError(

                "Expecting an absolute path of the library: " + filename);

        }

        ClassLoader.loadLibrary(fromClass, file);

    }

    /**

     * Loads the native library specified by the {@code libname}

     * argument.  The {@code libname} argument must not contain any platform

     * specific prefix, file extension or path. If a native library

     * called {@code libname} is statically linked with the VM, then the

     * JNI_OnLoad_{@code libname} function exported by the library is invoked.

     * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>

     * for more details.

     *

     * Otherwise, the libname argument is loaded from a system library

     * location and mapped to a native library image in an

     * implementation-dependent manner.

     * <p>

     * First, if there is a security manager, its {@code checkLink}

     * method is called with the {@code libname} 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}) 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.

     * @throws     SecurityException  if a security manager exists and its

     *             {@code checkLink} method doesn't allow

     *             loading of the specified dynamic library

     * @throws     UnsatisfiedLinkError if either the libname argument

     *             contains a file path, the native library is not statically

     *             linked with the VM,  or the library cannot be mapped to a

     *             native library image by the host system.

     * @throws     NullPointerException if {@code libname} is

     *             {@code null}

     * @see        java.lang.SecurityException

     * @see        java.lang.SecurityManager#checkLink(java.lang.String)

     */

    @CallerSensitive

    public void loadLibrary(String libname) {

        loadLibrary0(Reflection.getCallerClass(), libname);

    }

    void loadLibrary0(Class<?> fromClass, String libname) {

        @SuppressWarnings("removal")

        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);

    }

    /**

     * Returns the version of the Java Runtime Environment as a {@link Version}.

     *

     * @return  the {@link Version} of the Java Runtime Environment

     *

     * @since  9

     */

    public static Version version() {

        var v = version;

        if (v == null) {

            v = new Version(VersionProps.versionNumbers(),

                    VersionProps.pre(), VersionProps.build(),

                    VersionProps.optional());

            version = v;

        }

        return v;

    }

    /**

     * A representation of a version string for an implementation of the

     * Java SE Platform.  A version string consists of a version number

     * optionally followed by pre-release and build information.

     *

     * <h2><a id="verNum">Version numbers</a></h2>

     *

     * <p> A <em>version number</em>, {@code $VNUM}, is a non-empty sequence of

     * elements separated by period characters (U+002E).  An element is either

     * zero, or an unsigned integer numeral without leading zeros.  The final

     * element in a version number must not be zero.  When an element is

     * incremented, all subsequent elements are removed.  The format is: </p>

     *

     * <blockquote><pre>

     * [1-9][0-9]*((\.0)*\.[1-9][0-9]*)*

     * </pre></blockquote>

     *

     * <p> The sequence may be of arbitrary length but the first four elements

     * are assigned specific meanings, as follows:</p>

     *

     * <blockquote><pre>

     * $FEATURE.$INTERIM.$UPDATE.$PATCH

     * </pre></blockquote>

     *

     * <ul>

     *

     * <li><p> <a id="FEATURE">{@code $FEATURE}</a> &#x2014; The

     * feature-release counter, incremented for every feature release

     * regardless of release content.  Features may be added in a feature

     * release; they may also be removed, if advance notice was given at least

     * one feature release ahead of time.  Incompatible changes may be made

     * when justified. </p></li>

     *

     * <li><p> <a id="INTERIM">{@code $INTERIM}</a> &#x2014; The

     * interim-release counter, incremented for non-feature releases that

     * contain compatible bug fixes and enhancements but no incompatible

     * changes, no feature removals, and no changes to standard APIs.

     * </p></li>

     *

     * <li><p> <a id="UPDATE">{@code $UPDATE}</a> &#x2014; The update-release

     * counter, incremented for compatible update releases that fix security

     * issues, regressions, and bugs in newer features. </p></li>

     *

     * <li><p> <a id="PATCH">{@code $PATCH}</a> &#x2014; The emergency

     * patch-release counter, incremented only when it's necessary to produce

     * an emergency release to fix a critical issue. </p></li>

     *

     * </ul>

     *

     * <p> The fifth and later elements of a version number are free for use by

     * platform implementors, to identify implementor-specific patch

     * releases. </p>

     *

     * <p> A version number never has trailing zero elements.  If an element

     * and all those that follow it logically have the value zero then all of

     * them are omitted. </p>

     *

     * <p> The sequence of numerals in a version number is compared to another

     * such sequence in numerical, pointwise fashion; <em>e.g.</em>, {@code

     * 10.0.4} is less than {@code 10.1.2}.  If one sequence is shorter than

     * another then the missing elements of the shorter sequence are considered

     * to be less than the corresponding elements of the longer sequence;

     * <em>e.g.</em>, {@code 10.0.2} is less than {@code 10.0.2.1}. </p>

     *

     * <h2><a id="verStr">Version strings</a></h2>

     *

     * <p> A <em>version string</em>, {@code $VSTR}, is a version number {@code

     * $VNUM}, as described above, optionally followed by pre-release and build

     * information, in one of the following formats: </p>

     *

     * <blockquote><pre>

     *     $VNUM(-$PRE)?\+$BUILD(-$OPT)?

     *     $VNUM-$PRE(-$OPT)?

     *     $VNUM(\+-$OPT)?

     * </pre></blockquote>

     *

     * <p> where: </p>

     *

     * <ul>

     *

     * <li><p> <a id="pre">{@code $PRE}</a>, matching {@code ([a-zA-Z0-9]+)}

     * — A pre-release identifier.  Typically {@code ea}, for a

     * potentially unstable early-access release under active development, or

     * {@code internal}, for an internal developer build. </p></li>

     *

     * <li><p> <a id="build">{@code $BUILD}</a>, matching {@code

     * (0|[1-9][0-9]*)} — The build number, incremented for each promoted

     * build.  {@code $BUILD} is reset to {@code 1} when any portion of {@code

     * $VNUM} is incremented. </p></li>

     *

     * <li><p> <a id="opt">{@code $OPT}</a>, matching {@code ([-a-zA-Z0-9.]+)}

     * — Additional build information, if desired.  In the case of an

     * {@code internal} build this will often contain the date and time of the

     * build. </p></li>

     *

     * </ul>

     *

     * <p> A version string {@code 10-ea} matches {@code $VNUM = "10"} and

     * {@code $PRE = "ea"}.  The version string {@code 10+-ea} matches

     * {@code $VNUM = "10"} and {@code $OPT = "ea"}. </p>

     *

     * <p> When comparing two version strings, the value of {@code $OPT}, if

     * present, may or may not be significant depending on the chosen

     * comparison method.  The comparison methods {@link #compareTo(Version)

     * compareTo()} and {@link #compareToIgnoreOptional(Version)

     * compareToIgnoreOptional()} should be used consistently with the

     * corresponding methods {@link #equals(Object) equals()} and {@link

     * #equalsIgnoreOptional(Object) equalsIgnoreOptional()}.  </p>

     *

     * <p> A <em>short version string</em>, {@code $SVSTR}, often useful in

     * less formal contexts, is a version number optionally followed by a

     * pre-release identifier:</p>

     *

     * <blockquote><pre>

     *     $VNUM(-$PRE)?

     * </pre></blockquote>

     *

     * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>

     * class; programmers should treat instances that are

     * {@linkplain #equals(Object) equal} as interchangeable and should not

     * use instances for synchronization, or unpredictable behavior may

     * occur. For example, in a future release, synchronization may fail.</p>

     *

     * @since  9

     */

    @jdk.internal.ValueBased

    public static final class Version

        implements Comparable<Version>

    {

        private final List<Integer>     version;

        private final Optional<String>  pre;

        private final Optional<Integer> build;

        private final Optional<String>  optional;

        /*

         * List of version number components passed to this constructor MUST

         * be at least unmodifiable (ideally immutable). In the case of an

         * unmodifiable list, the caller MUST hand the list over to this

         * constructor and never change the underlying list.

         */

        private Version(List<Integer> unmodifiableListOfVersions,

                        Optional<String> pre,

                        Optional<Integer> build,

                        Optional<String> optional)

        {

            this.version = unmodifiableListOfVersions;

            this.pre = pre;

            this.build = build;

            this.optional = optional;

        }

        /**

         * Parses the given string as a valid

         * <a href="#verStr">version string</a> containing a

         * <a href="#verNum">version number</a> followed by pre-release and

         * build information.

         *

         * @param  s

         *         A string to interpret as a version

         *

         * @throws  IllegalArgumentException

         *          If the given string cannot be interpreted as a valid

         *          version

         *

         * @throws  NullPointerException

         *          If the given string is {@code null}

         *

         * @throws  NumberFormatException

         *          If an element of the version number or the build number

         *          cannot be represented as an {@link Integer}

         *

         * @return  The Version of the given string

         */

        public static Version parse(String s) {

            if (s == null)

                throw new NullPointerException();

            // Shortcut to avoid initializing VersionPattern when creating

            // feature-version constants during startup

            if (isSimpleNumber(s)) {

                return new Version(List.of(Integer.parseInt(s)),

                        Optional.empty(), Optional.empty(), Optional.empty());

            }

            Matcher m = VersionPattern.VSTR_PATTERN.matcher(s);

            if (!m.matches())

                throw new IllegalArgumentException("Invalid version string: '"

                                                   + s + "'");

            // $VNUM is a dot-separated list of integers of arbitrary length

            String[] split = m.group(VersionPattern.VNUM_GROUP).split("\\.");

            Integer[] version = new Integer[split.length];

            for (int i = 0; i < split.length; i++) {

                version[i] = Integer.parseInt(split[i]);

            }

            Optional<String> pre = Optional.ofNullable(

                    m.group(VersionPattern.PRE_GROUP));

            String b = m.group(VersionPattern.BUILD_GROUP);

            // $BUILD is an integer

            Optional<Integer> build = (b == null)

                ? Optional.empty()

                : Optional.of(Integer.parseInt(b));

            Optional<String> optional = Optional.ofNullable(

                    m.group(VersionPattern.OPT_GROUP));

            // empty '+'

            if (!build.isPresent()) {

                if (m.group(VersionPattern.PLUS_GROUP) != null) {

                    if (optional.isPresent()) {

                        if (pre.isPresent())

                            throw new IllegalArgumentException("'+' found with"

                                + " pre-release and optional components:'" + s

                                + "'");

                    } else {

                        throw new IllegalArgumentException("'+' found with neither"

                            + " build or optional components: '" + s + "'");

                    }

                } else {

                    if (optional.isPresent() && !pre.isPresent()) {

                        throw new IllegalArgumentException("optional component"

                            + " must be preceded by a pre-release component"

                            + " or '+': '" + s + "'");

                    }

                }

            }

            return new Version(List.of(version), pre, build, optional);

        }

        private static boolean isSimpleNumber(String s) {

            for (int i = 0; i < s.length(); i++) {

                char c = s.charAt(i);

                char lowerBound = (i > 0) ? '0' : '1';

                if (c < lowerBound || c > '9') {

                    return false;

                }

            }

            return true;

        }

        /**

         * Returns the value of the <a href="#FEATURE">feature</a> element of

         * the version number.

         *

         * @return The value of the feature element

         *

         * @since 10

         */

        public int feature() {

            return version.get(0);

        }

        /**

         * Returns the value of the <a href="#INTERIM">interim</a> element of

         * the version number, or zero if it is absent.

         *

         * @return The value of the interim element, or zero

         *

         * @since 10

         */

        public int interim() {

            return (version.size() > 1 ? version.get(1) : 0);

        }

        /**

         * Returns the value of the <a href="#UPDATE">update</a> element of the

         * version number, or zero if it is absent.

         *

         * @return The value of the update element, or zero

         *

         * @since 10

         */

        public int update() {

            return (version.size() > 2 ? version.get(2) : 0);

        }

        /**

         * Returns the value of the <a href="#PATCH">patch</a> element of the

         * version number, or zero if it is absent.

         *

         * @return The value of the patch element, or zero

         *

         * @since 10

         */

        public int patch() {

            return (version.size() > 3 ? version.get(3) : 0);

        }

        /**

         * Returns the value of the major element of the version number.

         *

         * @deprecated As of Java SE 10, the first element of a version

         * number is not the major-release number but the feature-release

         * counter, incremented for every time-based release.  Use the {@link

         * #feature()} method in preference to this method.  For compatibility,

         * this method returns the value of the <a href="#FEATURE">feature</a>

         * element.

         *

         * @return The value of the feature element

         */

        @Deprecated(since = "10")

        public int major() {

            return feature();

        }

        /**

         * Returns the value of the minor element of the version number, or

         * zero if it is absent.

         *

         * @deprecated As of Java SE 10, the second element of a version

         * number is not the minor-release number but the interim-release

         * counter, incremented for every interim release.  Use the {@link

         * #interim()} method in preference to this method.  For compatibility,

         * this method returns the value of the <a href="#INTERIM">interim</a>

         * element, or zero if it is absent.

         *

         * @return The value of the interim element, or zero

         */

        @Deprecated(since = "10")

        public int minor() {

            return interim();

        }

        /**

         * Returns the value of the security element of the version number, or

         * zero if it is absent.

         *

         * @deprecated As of Java SE 10, the third element of a version

         * number is not the security level but the update-release counter,

         * incremented for every update release.  Use the {@link #update()}

         * method in preference to this method.  For compatibility, this method

         * returns the value of the <a href="#UPDATE">update</a> element, or

         * zero if it is absent.

         *

         * @return  The value of the update element, or zero

         */

        @Deprecated(since = "10")

        public int security() {

            return update();

        }

        /**

         * Returns an unmodifiable {@link java.util.List List} of the integers

         * represented in the <a href="#verNum">version number</a>.

         * The {@code List} always contains at least one element corresponding to

         * the <a href="#FEATURE">feature version number</a>.

         *

         * @return  An unmodifiable list of the integers

         *          represented in the version number

         */

        public List<Integer> version() {

            return version;

        }

        /**

         * Returns the optional <a href="#pre">pre-release</a> information.

         *

         * @return  The optional pre-release information as a String

         */

        public Optional<String> pre() {