/*
 * Copyright (c) 1995, 2018, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.lang;

import java.io.*;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.StringTokenizer;

import jdk.internal.misc.SharedSecrets;
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.
 *
 * @author unascribed
 * @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) {
 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}("shutdownHooks")
 *
 * @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.
 *
 * @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}("shutdownHooks")
 *
 * @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
 * {@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) {
 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 {@link 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.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
 * {@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.
 * 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} stands for "garbage
 * collector". The 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();
 }

 /**
 * Not implemented, does nothing.
 *
 * @deprecated
 * This method was intended to control instruction tracing.
 * It has been superseded by JVM-specific tracing mechanisms.
 * This method is subject to removal in a future version of Java SE.
 *
 * @param on ignored
 */
 @Deprecated(since="9", forRemoval=true)
 public void traceInstructions(boolean on) { }

 /**
 * Not implemented, does nothing.
 *
 * @deprecated
 * This method was intended to control method call tracing.
 * It has been superseded by JVM-specific tracing mechanisms.
 * This method is subject to removal in a future version of Java SE.
 *
 * @param on ignored
 */
 @Deprecated(since="9", forRemoval=true)
 public void traceMethodCalls(boolean on) { }

 /**
 * 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);
 }

 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 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);
 }

 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);
 }

 /**
 * 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() {
 if (version == null) {
 version = new Version(VersionProps.versionNumbers(),
 VersionProps.pre(), VersionProps.build(),
 VersionProps.optional());
 }
 return version;
 }

 /**
 * A representation of a version string for an implementation of the
 * Java&nbsp;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]+)}
 * &#x2014; 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]*)} &#x2014; 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.]+)}
 * &#x2014; 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="./doc-files/ValueBased.html">value-based</a>
 * class; use of identity-sensitive operations (including reference equality
 * ({@code ==}), identity hash code, or synchronization) on instances of
 * {@code Version} may have unpredictable results and should be avoided.
 * </p>
 *
 * @since 9
 */
 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 on 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 preceeded 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&nbsp;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&nbsp;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&nbsp;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() {
 return pre;
 }

 /**
 * Returns the <a href="#build">build number</a>.
 *
 * @return The optional build number.
 */
 public Optional<Integer> build() {
 return build;
 }

 /**
 * Returns <a href="#opt">optional</a> additional identifying build
 * information.
 *
 * @return Additional build information as a String
 */
 public Optional<String> optional() {
 return optional;
 }

 /**
 * Compares this version to another.
 *
 * <p> Each of the components in the <a href="#verStr">version</a> is
 * compared in the following order of precedence: version numbers,
 * pre-release identifiers, build numbers, optional build information.
 * </p>
 *
 * <p> Comparison begins by examining the sequence of version numbers.
 * 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. </p>
 *
 * <p> A version with a pre-release identifier is always considered to
 * be less than a version without one. Pre-release identifiers are
 * compared numerically when they consist only of digits, and
 * lexicographically otherwise. Numeric identifiers are considered to
 * be less than non-numeric identifiers. </p>
 *
 * <p> A version without a build number is always less than one with a
 * build number; otherwise build numbers are compared numerically. </p>
 *
 * <p> The optional build information is compared lexicographically.
 * During this comparison, a version with optional build information is
 * considered to be greater than a version without one. </p>
 *
 * @param obj
 * The object to be compared
 *
 * @return A negative integer, zero, or a positive integer if this
 * {@code Version} is less than, equal to, or greater than the
 * given {@code Version}
 *
 * @throws NullPointerException
 * If the given object is {@code null}
 */
 @Override
 public int compareTo(Version obj) {
 return compare(obj, false);
 }

 /**
 * Compares this version to another disregarding optional build
 * information.
 *
 * <p> Two versions are compared by examining the version string as
 * described in {@link #compareTo(Version)} with the exception that the
 * optional build information is always ignored. </p>
 *
 * <p> This method provides ordering which is consistent with
 * {@code equalsIgnoreOptional()}. </p>
 *
 * @param obj
 * The object to be compared
 *
 * @return A negative integer, zero, or a positive integer if this
 * {@code Version} is less than, equal to, or greater than the
 * given {@code Version}
 *
 * @throws NullPointerException
 * If the given object is {@code null}
 */
 public int compareToIgnoreOptional(Version obj) {
 return compare(obj, true);
 }

 private int compare(Version obj, boolean ignoreOpt) {
 if (obj == null)
 throw new NullPointerException();

 int ret = compareVersion(obj);
 if (ret != 0)
 return ret;

 ret = comparePre(obj);
 if (ret != 0)
 return ret;

 ret = compareBuild(obj);
 if (ret != 0)
 return ret;

 if (!ignoreOpt)
 return compareOptional(obj);

 return 0;
 }

 private int compareVersion(Version obj) {
 int size = version.size();
 int oSize = obj.version().size();
 int min = Math.min(size, oSize);
 for (int i = 0; i < min; i++) {
 int val = version.get(i);
 int oVal = obj.version().get(i);
 if (val != oVal)
 return val - oVal;
 }
 return size - oSize;
 }

 private int comparePre(Version obj) {
 Optional<String> oPre = obj.pre();
 if (!pre.isPresent()) {
 if (oPre.isPresent())
 return 1;
 } else {
 if (!oPre.isPresent())
 return -1;
 String val = pre.get();
 String oVal = oPre.get();
 if (val.matches("\\d+")) {
 return (oVal.matches("\\d+")
 ? (new BigInteger(val)).compareTo(new BigInteger(oVal))
 : -1);
 } else {
 return (oVal.matches("\\d+")
 ? 1
 : val.compareTo(oVal));
 }
 }
 return 0;
 }

 private int compareBuild(Version obj) {
 Optional<Integer> oBuild = obj.build();
 if (oBuild.isPresent()) {
 return (build.isPresent()
 ? build.get().compareTo(oBuild.get())
 : -1);
 } else if (build.isPresent()) {
 return 1;
 }
 return 0;
 }

 private int compareOptional(Version obj) {
 Optional<String> oOpt = obj.optional();
 if (!optional.isPresent()) {
 if (oOpt.isPresent())
 return -1;
 } else {
 if (!oOpt.isPresent())
 return 1;
 return optional.get().compareTo(oOpt.get());
 }
 return 0;
 }

 /**
 * Returns a string representation of this version.
 *
 * @return The version string
 */
 @Override
 public String toString() {
 StringBuilder sb
 = new StringBuilder(version.stream()
 .map(Object::toString)
 .collect(Collectors.joining(".")));

 pre.ifPresent(v -> sb.append("-").append(v));

 if (build.isPresent()) {
 sb.append("+").append(build.get());
 if (optional.isPresent())
 sb.append("-").append(optional.get());
 } else {
 if (optional.isPresent()) {
 sb.append(pre.isPresent() ? "-" : "+-");
 sb.append(optional.get());
 }
 }

 return sb.toString();
 }

 /**
 * Determines whether this {@code Version} is equal to another object.
 *
 * <p> Two {@code Version}s are equal if and only if they represent the
 * same version string.
 *
 * @param obj
 * The object to which this {@code Version} is to be compared
 *
 * @return {@code true} if, and only if, the given object is a {@code
 * Version} that is identical to this {@code Version}
 *
 */
 @Override
 public boolean equals(Object obj) {
 boolean ret = equalsIgnoreOptional(obj);
 if (!ret)
 return false;

 Version that = (Version)obj;
 return (this.optional().equals(that.optional()));
 }

 /**
 * Determines whether this {@code Version} is equal to another
 * disregarding optional build information.
 *
 * <p> Two {@code Version}s are equal if and only if they represent the
 * same version string disregarding the optional build information.
 *
 * @param obj
 * The object to which this {@code Version} is to be compared
 *
 * @return {@code true} if, and only if, the given object is a {@code
 * Version} that is identical to this {@code Version}
 * ignoring the optional build information
 *
 */
 public boolean equalsIgnoreOptional(Object obj) {
 if (this == obj)
 return true;
 if (!(obj instanceof Version))
 return false;

 Version that = (Version)obj;
 return (this.version().equals(that.version())
 && this.pre().equals(that.pre())
 && this.build().equals(that.build()));
 }

 /**
 * Returns the hash code of this version.
 *
 * @return The hashcode of this version
 */
 @Override
 public int hashCode() {
 int h = 1;
 int p = 17;

 h = p * h + version.hashCode();
 h = p * h + pre.hashCode();
 h = p * h + build.hashCode();
 h = p * h + optional.hashCode();

 return h;
 }
 }

 private static class VersionPattern {
 // $VNUM(-$PRE)?(\+($BUILD)?(\-$OPT)?)?
 // RE limits the format of version strings
 // ([1-9][0-9]*(?:(?:\.0)*\.[1-9][0-9]*)*)(?:-([a-zA-Z0-9]+))?(?:(\+)(0|[1-9][0-9]*)?)?(?:-([-a-zA-Z0-9.]+))?

 private static final String VNUM
 = "(?<VNUM>[1-9][0-9]*(?:(?:\\.0)*\\.[1-9][0-9]*)*)";
 private static final String PRE = "(?:-(?<PRE>[a-zA-Z0-9]+))?";
 private static final String BUILD
 = "(?:(?<PLUS>\\+)(?<BUILD>0|[1-9][0-9]*)?)?";
 private static final String OPT = "(?:-(?<OPT>[-a-zA-Z0-9.]+))?";
 private static final String VSTR_FORMAT = VNUM + PRE + BUILD + OPT;

 static final Pattern VSTR_PATTERN = Pattern.compile(VSTR_FORMAT);

 static final String VNUM_GROUP = "VNUM";
 static final String PRE_GROUP = "PRE";
 static final String PLUS_GROUP = "PLUS";
 static final String BUILD_GROUP = "BUILD";
 static final String OPT_GROUP = "OPT";
 }
}