Java tutorial
/* * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.io.*; import java.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.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.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. * <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); } 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 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> — 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> — 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> — 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> — 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="./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 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() { 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"; } }