System
/* * @(#)System.java 1.159 07/11/27 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.lang; import java.io.*; import java.util.Properties; import java.util.PropertyPermission; import java.util.StringTokenizer; import java.security.AccessController; import java.security.PrivilegedAction; import java.security.AllPermission; import java.nio.channels.Channel; import java.nio.channels.spi.SelectorProvider; import sun.nio.ch.Interruptible; import sun.net.InetAddressCachePolicy; import sun.reflect.Reflection; import sun.security.util.SecurityConstants; import sun.reflect.annotation.AnnotationType; /** * The <code>System</code> class contains several useful class fields * and methods. It cannot be instantiated. * * <p>Among the facilities provided by the <code>System</code> class * are standard input, standard output, and error output streams; * access to externally defined properties and environment * variables; a means of loading files and libraries; and a utility * method for quickly copying a portion of an array. * * @author unascribed * @version 1.159, 11/27/07 * @since JDK1.0 */ public final class System { /* First thing---register the natives */ private static native void registerNatives(); static { registerNatives(); } /** Don't let anyone instantiate this class */ private System() { } /** * The "standard" input stream. This stream is already * open and ready to supply input data. Typically this stream * corresponds to keyboard input or another input source specified by * the host environment or user. */ public final static InputStream in = nullInputStream(); /** * The "standard" output stream. This stream is already * open and ready to accept output data. Typically this stream * corresponds to display output or another output destination * specified by the host environment or user. * <p> * For simple stand-alone Java applications, a typical way to write * a line of output data is: * <blockquote><pre> * System.out.println(data) * </pre></blockquote> * <p> * See the <code>println</code> methods in class <code>PrintStream</code>. * * @see java.io.PrintStream#println() * @see java.io.PrintStream#println(boolean) * @see java.io.PrintStream#println(char) * @see java.io.PrintStream#println(char[]) * @see java.io.PrintStream#println(double) * @see java.io.PrintStream#println(float) * @see java.io.PrintStream#println(int) * @see java.io.PrintStream#println(long) * @see java.io.PrintStream#println(java.lang.Object) * @see java.io.PrintStream#println(java.lang.String) */ public final static PrintStream out = nullPrintStream(); /** * The "standard" error output stream. This stream is already * open and ready to accept output data. * <p> * Typically this stream corresponds to display output or another * output destination specified by the host environment or user. By * convention, this output stream is used to display error messages * or other information that should come to the immediate attention * of a user even if the principal output stream, the value of the * variable <code>out</code>, has been redirected to a file or other * destination that is typically not continuously monitored. */ public final static PrintStream err = nullPrintStream(); /* The security manager for the system. */ private static volatile SecurityManager security = null; /** * Reassigns the "standard" input stream. * * <p>First, if there is a security manager, its <code>checkPermission</code> * method is called with a <code>RuntimePermission("setIO")</code> permission * to see if it's ok to reassign the "standard" input stream. * <p> * * @param in the new standard input stream. * * @throws SecurityException * if a security manager exists and its * <code>checkPermission</code> method doesn't allow * reassigning of the standard input stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setIn(InputStream in) { checkIO(); setIn0(in); } /** * Reassigns the "standard" output stream. * * <p>First, if there is a security manager, its <code>checkPermission</code> * method is called with a <code>RuntimePermission("setIO")</code> permission * to see if it's ok to reassign the "standard" output stream. * * @param out the new standard output stream * * @throws SecurityException * if a security manager exists and its * <code>checkPermission</code> method doesn't allow * reassigning of the standard output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setOut(PrintStream out) { checkIO(); setOut0(out); } /** * Reassigns the "standard" error output stream. * * <p>First, if there is a security manager, its <code>checkPermission</code> * method is called with a <code>RuntimePermission("setIO")</code> permission * to see if it's ok to reassign the "standard" error output stream. * * @param err the new standard error output stream. * * @throws SecurityException * if a security manager exists and its * <code>checkPermission</code> method doesn't allow * reassigning of the standard error output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setErr(PrintStream err) { checkIO(); setErr0(err); } private static volatile Console cons = null; /** * Returns the unique {@link java.io.Console Console} object associated * with the current Java virtual machine, if any. * * @return The system console, if any, otherwise <tt>null</tt>. * * @since 1.6 */ public static Console console() { if (cons == null) { synchronized (System.class) { cons = sun.misc.SharedSecrets.getJavaIOAccess().console(); } } return cons; } /** * Returns the channel inherited from the entity that created this * Java virtual machine. * * <p> This method returns the channel obtained by invoking the * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel} method of the system-wide default * {@link java.nio.channels.spi.SelectorProvider} object. </p> * * <p> In addition to the network-oriented channels described in * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel}, this method may return other kinds of * channels in the future. * * @return The inherited channel, if any, otherwise <tt>null</tt>. * * @throws IOException * If an I/O error occurs * * @throws SecurityException * If a security manager is present and it does not * permit access to the channel. * * @since 1.5 */ public static Channel inheritedChannel() throws IOException { return SelectorProvider.provider().inheritedChannel(); } private static void checkIO() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("setIO")); } } private static native void setIn0(InputStream in); private static native void setOut0(PrintStream out); private static native void setErr0(PrintStream err); /** * Sets the System security. * * <p> If there is a security manager already installed, this method first * calls the security manager's <code>checkPermission</code> method * with a <code>RuntimePermission("setSecurityManager")</code> * permission to ensure it's ok to replace the existing * security manager. * This may result in throwing a <code>SecurityException</code>. * * <p> Otherwise, the argument is established as the current * security manager. If the argument is <code>null</code> and no * security manager has been established, then no action is taken and * the method simply returns. * * @param s the security manager. * @exception SecurityException if the security manager has already * been set and its <code>checkPermission</code> method * doesn't allow it to be replaced. * @see #getSecurityManager * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission */ public static void setSecurityManager(final SecurityManager s) { try { s.checkPackageAccess("java.lang"); } catch (Exception e) { // no-op } setSecurityManager0(s); } private static synchronized void setSecurityManager0(final SecurityManager s) { SecurityManager sm = getSecurityManager(); if (sm != null) { // ask the currently installed security manager if we // can replace it. sm.checkPermission(new RuntimePermission ("setSecurityManager")); } if ((s != null) && (s.getClass().getClassLoader() != null)) { // New security manager class is not on bootstrap classpath. // Cause policy to get initialized before we install the new // security manager, in order to prevent infinite loops when // trying to initialize the policy (which usually involves // accessing some security and/or system properties, which in turn // calls the installed security manager's checkPermission method // which will loop infinitely if there is a non-system class // (in this case: the new security manager class) on the stack). AccessController.doPrivileged(new PrivilegedAction() { public Object run() { s.getClass().getProtectionDomain().implies (SecurityConstants.ALL_PERMISSION); return null; } }); } security = s; InetAddressCachePolicy.setIfNotSet(InetAddressCachePolicy.FOREVER); } /** * Gets the system security interface. * * @return if a security manager has already been established for the * current application, then that security manager is returned; * otherwise, <code>null</code> is returned. * @see #setSecurityManager */ public static SecurityManager getSecurityManager() { return security; } /** * Returns the current time in milliseconds. Note that * while the unit of time of the return value is a millisecond, * the granularity of the value depends on the underlying * operating system and may be larger. For example, many * operating systems measure time in units of tens of * milliseconds. * * <p> See the description of the class <code>Date</code> for * a discussion of slight discrepancies that may arise between * "computer time" and coordinated universal time (UTC). * * @return the difference, measured in milliseconds, between * the current time and midnight, January 1, 1970 UTC. * @see java.util.Date */ public static native long currentTimeMillis(); /** * Returns the current value of the most precise available system * timer, in nanoseconds. * * <p>This method can only be used to measure elapsed time and is * not related to any other notion of system or wall-clock time. * The value returned represents nanoseconds since some fixed but * arbitrary time (perhaps in the future, so values may be * negative). This method provides nanosecond precision, but not * necessarily nanosecond accuracy. No guarantees are made about * how frequently values change. Differences in successive calls * that span greater than approximately 292 years (2<sup>63</sup> * nanoseconds) will not accurately compute elapsed time due to * numerical overflow. * * <p> For example, to measure how long some code takes to execute: * <pre> * long startTime = System.nanoTime(); * // ... the code being measured ... * long estimatedTime = System.nanoTime() - startTime; * </pre> * * @return The current value of the system timer, in nanoseconds. * @since 1.5 */ public static native long nanoTime(); /** * Copies an array from the specified source array, beginning at the * specified position, to the specified position of the destination array. * A subsequence of array components are copied from the source * array referenced by <code>src</code> to the destination array * referenced by <code>dest</code>. The number of components copied is * equal to the <code>length</code> argument. The components at * positions <code>srcPos</code> through * <code>srcPos+length-1</code> in the source array are copied into * positions <code>destPos</code> through * <code>destPos+length-1</code>, respectively, of the destination * array. * <p> * If the <code>src</code> and <code>dest</code> arguments refer to the * same array object, then the copying is performed as if the * components at positions <code>srcPos</code> through * <code>srcPos+length-1</code> were first copied to a temporary * array with <code>length</code> components and then the contents of * the temporary array were copied into positions * <code>destPos</code> through <code>destPos+length-1</code> of the * destination array. * <p> * If <code>dest</code> is <code>null</code>, then a * <code>NullPointerException</code> is thrown. * <p> * If <code>src</code> is <code>null</code>, then a * <code>NullPointerException</code> is thrown and the destination * array is not modified. * <p> * Otherwise, if any of the following is true, an * <code>ArrayStoreException</code> is thrown and the destination is * not modified: * <ul> * <li>The <code>src</code> argument refers to an object that is not an * array. * <li>The <code>dest</code> argument refers to an object that is not an * array. * <li>The <code>src</code> argument and <code>dest</code> argument refer * to arrays whose component types are different primitive types. * <li>The <code>src</code> argument refers to an array with a primitive * component type and the <code>dest</code> argument refers to an array * with a reference component type. * <li>The <code>src</code> argument refers to an array with a reference * component type and the <code>dest</code> argument refers to an array * with a primitive component type. * </ul> * <p> * Otherwise, if any of the following is true, an * <code>IndexOutOfBoundsException</code> is * thrown and the destination is not modified: * <ul> * <li>The <code>srcPos</code> argument is negative. * <li>The <code>destPos</code> argument is negative. * <li>The <code>length</code> argument is negative. * <li><code>srcPos+length</code> is greater than * <code>src.length</code>, the length of the source array. * <li><code>destPos+length</code> is greater than * <code>dest.length</code>, the length of the destination array. * </ul> * <p> * Otherwise, if any actual component of the source array from * position <code>srcPos</code> through * <code>srcPos+length-1</code> cannot be converted to the component * type of the destination array by assignment conversion, an * <code>ArrayStoreException</code> is thrown. In this case, let * <b><i>k</i></b> be the smallest nonnegative integer less than * length such that <code>src[srcPos+</code><i>k</i><code>]</code> * cannot be converted to the component type of the destination * array; when the exception is thrown, source array components from * positions <code>srcPos</code> through * <code>srcPos+</code><i>k</i><code>-1</code> * will already have been copied to destination array positions * <code>destPos</code> through * <code>destPos+</code><i>k</I><code>-1</code> and no other * positions of the destination array will have been modified. * (Because of the restrictions already itemized, this * paragraph effectively applies only to the situation where both * arrays have component types that are reference types.) * * @param src the source array. * @param srcPos starting position in the source array. * @param dest the destination array. * @param destPos starting position in the destination data. * @param length the number of array elements to be copied. * @exception IndexOutOfBoundsException if copying would cause * access of data outside array bounds. * @exception ArrayStoreException if an element in the <code>src</code> * array could not be stored into the <code>dest</code> array * because of a type mismatch. * @exception NullPointerException if either <code>src</code> or * <code>dest</code> is <code>null</code>. */ public static native void arraycopy(Object src, int srcPos, Object dest, int destPos, int length); /** * Returns the same hash code for the given object as * would be returned by the default method hashCode(), * whether or not the given object's class overrides * hashCode(). * The hash code for the null reference is zero. * * @param x object for which the hashCode is to be calculated * @return the hashCode * @since JDK1.1 */ public static native int identityHashCode(Object x); /** * System properties. The following properties are guaranteed to be defined: * <dl> * <dt>java.version <dd>Java version number * <dt>java.vendor <dd>Java vendor specific string * <dt>java.vendor.url <dd>Java vendor URL * <dt>java.home <dd>Java installation directory * <dt>java.class.version <dd>Java class version number * <dt>java.class.path <dd>Java classpath * <dt>os.name <dd>Operating System Name * <dt>os.arch <dd>Operating System Architecture * <dt>os.version <dd>Operating System Version * <dt>file.separator <dd>File separator ("/" on Unix) * <dt>path.separator <dd>Path separator (":" on Unix) * <dt>line.separator <dd>Line separator ("/n" on Unix) * <dt>user.name <dd>User account name * <dt>user.home <dd>User home directory * <dt>user.dir <dd>User's current working directory * </dl> */ private static Properties props; private static native Properties initProperties(Properties props); /** * Determines the current system properties. * <p> * First, if there is a security manager, its * <code>checkPropertiesAccess</code> method is called with no * arguments. This may result in a security exception. * <p> * The current set of system properties for use by the * {@link #getProperty(String)} method is returned as a * <code>Properties</code> object. If there is no current set of * system properties, a set of system properties is first created and * initialized. This set of system properties always includes values * for the following keys: * <table summary="Shows property keys and associated values"> * <tr><th>Key</th> * <th>Description of Associated Value</th></tr> * <tr><td><code>java.version</code></td> * <td>Java Runtime Environment version</td></tr> * <tr><td><code>java.vendor</code></td> * <td>Java Runtime Environment vendor</td></tr * <tr><td><code>java.vendor.url</code></td> * <td>Java vendor URL</td></tr> * <tr><td><code>java.home</code></td> * <td>Java installation directory</td></tr> * <tr><td><code>java.vm.specification.version</code></td> * <td>Java Virtual Machine specification version</td></tr> * <tr><td><code>java.vm.specification.vendor</code></td> * <td>Java Virtual Machine specification vendor</td></tr> * <tr><td><code>java.vm.specification.name</code></td> * <td>Java Virtual Machine specification name</td></tr> * <tr><td><code>java.vm.version</code></td> * <td>Java Virtual Machine implementation version</td></tr> * <tr><td><code>java.vm.vendor</code></td> * <td>Java Virtual Machine implementation vendor</td></tr> * <tr><td><code>java.vm.name</code></td> * <td>Java Virtual Machine implementation name</td></tr> * <tr><td><code>java.specification.version</code></td> * <td>Java Runtime Environment specification version</td></tr> * <tr><td><code>java.specification.vendor</code></td> * <td>Java Runtime Environment specification vendor</td></tr> * <tr><td><code>java.specification.name</code></td> * <td>Java Runtime Environment specification name</td></tr> * <tr><td><code>java.class.version</code></td> * <td>Java class format version number</td></tr> * <tr><td><code>java.class.path</code></td> * <td>Java class path</td></tr> * <tr><td><code>java.library.path</code></td> * <td>List of paths to search when loading libraries</td></tr> * <tr><td><code>java.io.tmpdir</code></td> * <td>Default temp file path</td></tr> * <tr><td><code>java.compiler</code></td> * <td>Name of JIT compiler to use</td></tr> * <tr><td><code>java.ext.dirs</code></td> * <td>Path of extension directory or directories</td></tr> * <tr><td><code>os.name</code></td> * <td>Operating system name</td></tr> * <tr><td><code>os.arch</code></td> * <td>Operating system architecture</td></tr> * <tr><td><code>os.version</code></td> * <td>Operating system version</td></tr> * <tr><td><code>file.separator</code></td> * <td>File separator ("/" on UNIX)</td></tr> * <tr><td><code>path.separator</code></td> * <td>Path separator (":" on UNIX)</td></tr> * <tr><td><code>line.separator</code></td> * <td>Line separator ("/n" on UNIX)</td></tr> * <tr><td><code>user.name</code></td> * <td>User's account name</td></tr> * <tr><td><code>user.home</code></td> * <td>User's home directory</td></tr> * <tr><td><code>user.dir</code></td> * <td>User's current working directory</td></tr> * </table> * <p> * Multiple paths in a system property value are separated by the path * separator character of the platform. * <p> * Note that even if the security manager does not permit the * <code>getProperties</code> operation, it may choose to permit the * {@link #getProperty(String)} operation. * * @return the system properties * @exception SecurityException if a security manager exists and its * <code>checkPropertiesAccess</code> method doesn't allow access * to the system properties. * @see #setProperties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() * @see java.util.Properties */ public static Properties getProperties() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertiesAccess(); } return props; } /** * Sets the system properties to the <code>Properties</code> * argument. * <p> * First, if there is a security manager, its * <code>checkPropertiesAccess</code> method is called with no * arguments. This may result in a security exception. * <p> * The argument becomes the current set of system properties for use * by the {@link #getProperty(String)} method. If the argument is * <code>null</code>, then the current set of system properties is * forgotten. * * @param props the new system properties. * @exception SecurityException if a security manager exists and its * <code>checkPropertiesAccess</code> method doesn't allow access * to the system properties. * @see #getProperties * @see java.util.Properties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() */ public static void setProperties(Properties props) { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertiesAccess(); } if (props == null) { props = new Properties(); initProperties(props); } System.props = props; } /** * Gets the system property indicated by the specified key. * <p> * First, if there is a security manager, its * <code>checkPropertyAccess</code> method is called with the key as * its argument. This may result in a SecurityException. * <p> * If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the <code>getProperties</code> method. * * @param key the name of the system property. * @return the string value of the system property, * or <code>null</code> if there is no property with that key. * * @exception SecurityException if a security manager exists and its * <code>checkPropertyAccess</code> method doesn't allow * access to the specified system property. * @exception NullPointerException if <code>key</code> is * <code>null</code>. * @exception IllegalArgumentException if <code>key</code> is empty. * @see #setProperty * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static String getProperty(String key) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertyAccess(key); } return props.getProperty(key); } /** * Gets the system property indicated by the specified key. * <p> * First, if there is a security manager, its * <code>checkPropertyAccess</code> method is called with the * <code>key</code> as its argument. * <p> * If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the <code>getProperties</code> method. * * @param key the name of the system property. * @param def a default value. * @return the string value of the system property, * or the default value if there is no property with that key. * * @exception SecurityException if a security manager exists and its * <code>checkPropertyAccess</code> method doesn't allow * access to the specified system property. * @exception NullPointerException if <code>key</code> is * <code>null</code>. * @exception IllegalArgumentException if <code>key</code> is empty. * @see #setProperty * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static String getProperty(String key, String def) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertyAccess(key); } return props.getProperty(key, def); } /** * Sets the system property indicated by the specified key. * <p> * First, if a security manager exists, its * <code>SecurityManager.checkPermission</code> method * is called with a <code>PropertyPermission(key, "write")</code> * permission. This may result in a SecurityException being thrown. * If no exception is thrown, the specified property is set to the given * value. * <p> * * @param key the name of the system property. * @param value the value of the system property. * @return the previous value of the system property, * or <code>null</code> if it did not have one. * * @exception SecurityException if a security manager exists and its * <code>checkPermission</code> method doesn't allow * setting of the specified property. * @exception NullPointerException if <code>key</code> or * <code>value</code> is <code>null</code>. * @exception IllegalArgumentException if <code>key</code> is empty. * @see #getProperty * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) * @see java.util.PropertyPermission * @see SecurityManager#checkPermission * @since 1.2 */ public static String setProperty(String key, String value) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new PropertyPermission(key, SecurityConstants.PROPERTY_WRITE_ACTION)); } return (String) props.setProperty(key, value); } /** * Removes the system property indicated by the specified key. * <p> * First, if a security manager exists, its * <code>SecurityManager.checkPermission</code> method * is called with a <code>PropertyPermission(key, "write")</code> * permission. This may result in a SecurityException being thrown. * If no exception is thrown, the specified property is removed. * <p> * * @param key the name of the system property to be removed. * @return the previous string value of the system property, * or <code>null</code> if there was no property with that key. * * @exception SecurityException if a security manager exists and its * <code>checkPropertyAccess</code> method doesn't allow * access to the specified system property. * @exception NullPointerException if <code>key</code> is * <code>null</code>. * @exception IllegalArgumentException if <code>key</code> is empty. * @see #getProperty * @see #setProperty * @see java.util.Properties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() * @since 1.5 */ public static String clearProperty(String key) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new PropertyPermission(key, "write")); } return (String) props.remove(key); } private static void checkKey(String key) { if (key == null) { throw new NullPointerException("key can't be null"); } if (key.equals("")) { throw new IllegalArgumentException("key can't be empty"); } } /** * Gets the value of the specified environment variable. An * environment variable is a system-dependent external named * value. * * <p>If a security manager exists, its * {@link SecurityManager#checkPermission checkPermission} * method is called with a * <code>{@link RuntimePermission}("getenv."+name)</code> * permission. This may result in a {@link SecurityException} * being thrown. If no exception is thrown the value of the * variable <code>name</code> is returned. * * <p><a name="EnvironmentVSSystemProperties"><i>System * properties</i> and <i>environment variables</i></a> are both * conceptually mappings between names and values. Both * mechanisms can be used to pass user-defined information to a * Java process. Environment variables have a more global effect, * because they are visible to all descendants of the process * which defines them, not just the immediate Java subprocess. * They can have subtly different semantics, such as case * insensitivity, on different operating systems. For these * reasons, environment variables are more likely to have * unintended side effects. It is best to use system properties * where possible. Environment variables should be used when a * global effect is desired, or when an external system interface * requires an environment variable (such as <code>PATH</code>). * * <p>On UNIX systems the alphabetic case of <code>name</code> is * typically significant, while on Microsoft Windows systems it is * typically not. For example, the expression * <code>System.getenv("FOO").equals(System.getenv("foo"))</code> * is likely to be true on Microsoft Windows. * * @param name the name of the environment variable * @return the string value of the variable, or <code>null</code> * if the variable is not defined in the system environment * @throws NullPointerException if <code>name</code> is <code>null</code> * @throws SecurityException * if a security manager exists and its * {@link SecurityManager#checkPermission checkPermission} * method doesn't allow access to the environment variable * <code>name</code> * @see #getenv() * @see ProcessBuilder#environment() */ public static String getenv(String name) { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("getenv."+name)); } return ProcessEnvironment.getenv(name); } /** * Returns an unmodifiable string map view of the current system environment. * The environment is a system-dependent mapping from names to * values which is passed from parent to child processes. * * <p>If the system does not support environment variables, an * empty map is returned. * * <p>The returned map will never contain null keys or values. * Attempting to query the presence of a null key or value will * throw a {@link NullPointerException}. Attempting to query * the presence of a key or value which is not of type * {@link String} will throw a {@link ClassCastException}. * * <p>The returned map and its collection views may not obey the * general contract of the {@link Object#equals} and * {@link Object#hashCode} methods. * * <p>The returned map is typically case-sensitive on all platforms. * * <p>If a security manager exists, its * {@link SecurityManager#checkPermission checkPermission} * method is called with a * <code>{@link RuntimePermission}("getenv.*")</code> * permission. This may result in a {@link SecurityException} being * thrown. * * <p>When passing information to a Java subprocess, * <a href="#EnvironmentVSSystemProperties" mce_href="#EnvironmentVSSystemProperties">system properties</a> * are generally preferred over environment variables. * * @return the environment as a map of variable names to values * @throws SecurityException * if a security manager exists and its * {@link SecurityManager#checkPermission checkPermission} * method doesn't allow access to the process environment * @see #getenv(String) * @see ProcessBuilder#environment() * @since 1.5 */ public static java.util.Map<String,String> getenv() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("getenv.*")); } return ProcessEnvironment.getenv(); } /** * Terminates the currently running Java Virtual Machine. The * argument serves as a status code; by convention, a nonzero status * code indicates abnormal termination. * <p> * This method calls the <code>exit</code> method in class * <code>Runtime</code>. This method never returns normally. * <p> * The call <code>System.exit(n)</code> is effectively equivalent to * the call: * <blockquote><pre> * Runtime.getRuntime().exit(n) * </pre></blockquote> * * @param status exit status. * @throws SecurityException * if a security manager exists and its <code>checkExit</code> * method doesn't allow exit with the specified status. * @see java.lang.Runtime#exit(int) */ public static void exit(int status) { Runtime.getRuntime().exit(status); } /** * Runs the garbage collector. * <p> * Calling the <code>gc</code> 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 Java Virtual * Machine has made a best effort to reclaim space from all discarded * objects. * <p> * The call <code>System.gc()</code> is effectively equivalent to the * call: * <blockquote><pre> * Runtime.getRuntime().gc() * </pre></blockquote> * * @see java.lang.Runtime#gc() */ public static void gc() { Runtime.getRuntime().gc(); } /** * Runs the finalization methods of any objects pending finalization. * <p> * Calling this method suggests that the Java Virtual Machine expend * effort toward running the <code>finalize</code> methods of objects * that have been found to be discarded but whose <code>finalize</code> * methods have not yet been run. When control returns from the * method call, the Java Virtual Machine has made a best effort to * complete all outstanding finalizations. * <p> * The call <code>System.runFinalization()</code> is effectively * equivalent to the call: * <blockquote><pre> * Runtime.getRuntime().runFinalization() * </pre></blockquote> * * @see java.lang.Runtime#runFinalization() */ public static void runFinalization() { Runtime.getRuntime().runFinalization(); } /** * Enable or disable finalization on exit; doing so specifies that the * finalizers of all objects that have finalizers that have not yet been * automatically invoked are to be run before the Java runtime exits. * By default, finalization on exit is disabled. * * <p>If there is a security manager, * its <code>checkExit</code> method is first called * with 0 as its argument to ensure the exit is allowed. * This could result in a SecurityException. * * @deprecated This method is inherently unsafe. It may result in * finalizers being called on live objects while other threads are * concurrently manipulating those objects, resulting in erratic * behavior or deadlock. * @param value indicating enabling or disabling of finalization * @throws SecurityException * if a security manager exists and its <code>checkExit</code> * method doesn't allow the exit. * * @see java.lang.Runtime#exit(int) * @see java.lang.Runtime#gc() * @see java.lang.SecurityManager#checkExit(int) * @since JDK1.1 */ @Deprecated public static void runFinalizersOnExit(boolean value) { Runtime.getRuntime().runFinalizersOnExit(value); } /** * Loads a code file with the specified filename from the local file * system as a dynamic library. The filename * argument must be a complete path name. * <p> * The call <code>System.load(name)</code> is effectively equivalent * to the call: * <blockquote><pre> * Runtime.getRuntime().load(name) * </pre></blockquote> * * @param filename the file to load. * @exception SecurityException if a security manager exists and its * <code>checkLink</code> method doesn't allow * loading of the specified dynamic library * @exception UnsatisfiedLinkError if the file does not exist. * @exception NullPointerException if <code>filename</code> is * <code>null</code> * @see java.lang.Runtime#load(java.lang.String) * @see java.lang.SecurityManager#checkLink(java.lang.String) */ public static void load(String filename) { Runtime.getRuntime().load0(getCallerClass(), filename); } /** * Loads the system library specified by the <code>libname</code> * argument. The manner in which a library name is mapped to the * actual system library is system dependent. * <p> * The call <code>System.loadLibrary(name)</code> is effectively * equivalent to the call * <blockquote><pre> * Runtime.getRuntime().loadLibrary(name) * </pre></blockquote> * * @param libname the name of the library. * @exception SecurityException if a security manager exists and its * <code>checkLink</code> method doesn't allow * loading of the specified dynamic library * @exception UnsatisfiedLinkError if the library does not exist. * @exception NullPointerException if <code>libname</code> is * <code>null</code> * @see java.lang.Runtime#loadLibrary(java.lang.String) * @see java.lang.SecurityManager#checkLink(java.lang.String) */ public static void loadLibrary(String libname) { Runtime.getRuntime().loadLibrary0(getCallerClass(), libname); } /** * Maps a library name into a platform-specific string representing * a native library. * * @param libname the name of the library. * @return a platform-dependent native library name. * @exception NullPointerException if <code>libname</code> is * <code>null</code> * @see java.lang.System#loadLibrary(java.lang.String) * @see java.lang.ClassLoader#findLibrary(java.lang.String) * @since 1.2 */ public static native String mapLibraryName(String libname); /** * The following two methods exist because in, out, and err must be * initialized to null. The compiler, however, cannot be permitted to * inline access to them, since they are later set to more sensible values * by initializeSystemClass(). */ private static InputStream nullInputStream() throws NullPointerException { if (currentTimeMillis() > 0) { return null; } throw new NullPointerException(); } private static PrintStream nullPrintStream() throws NullPointerException { if (currentTimeMillis() > 0) { return null; } throw new NullPointerException(); } /** * Initialize the system class. Called after thread initialization. */ private static void initializeSystemClass() { props = new Properties(); initProperties(props); sun.misc.Version.init(); // Load the zip library now in order to keep java.util.zip.ZipFile // from trying to use itself to load this library later. loadLibrary("zip"); FileInputStream fdIn = new FileInputStream(FileDescriptor.in); FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out); FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err); setIn0(new BufferedInputStream(fdIn)); setOut0(new PrintStream(new BufferedOutputStream(fdOut, 128), true)); setErr0(new PrintStream(new BufferedOutputStream(fdErr, 128), true)); // Setup Java signal handlers for HUP, TERM, and INT (where available). Terminator.setup(); // The order in with the hooks are added here is important as it // determines the order in which they are run. // (1)Console restore hook needs to be called first. // (2)Application hooks must be run before calling deleteOnExitHook. Shutdown.add(sun.misc.SharedSecrets.getJavaIOAccess().consoleRestoreHook()); Shutdown.add(ApplicationShutdownHooks.hook()); Shutdown.add(sun.misc.SharedSecrets.getJavaIODeleteOnExitAccess()); // Initialize any miscellenous operating system settings that need to be // set for the class libraries. Currently this is no-op everywhere except // for Windows where the process-wide error mode is set before the java.io // classes are used. sun.misc.VM.initializeOSEnvironment(); // Set the maximum amount of direct memory. This value is controlled // by the vm option -XX:MaxDirectMemorySize=<size>. This method acts // as an initializer only if it is called before sun.misc.VM.booted(). sun.misc.VM.maxDirectMemory(); // Set a boolean to determine whether ClassLoader.loadClass accepts // array syntax. This value is controlled by the system property // "sun.lang.ClassLoader.allowArraySyntax". This method acts as // an initializer only if it is called before sun.misc.VM.booted(). sun.misc.VM.allowArraySyntax(); // Subsystems that are invoked during initialization can invoke // sun.misc.VM.isBooted() in order to avoid doing things that should // wait until the application class loader has been set up. sun.misc.VM.booted(); // The main thread is not added to its thread group in the same // way as other threads; we must do it ourselves here. Thread current = Thread.currentThread(); current.getThreadGroup().add(current); // Allow privileged classes outside of java.lang sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){ public sun.reflect.ConstantPool getConstantPool(Class klass) { return klass.getConstantPool(); } public void setAnnotationType(Class klass, AnnotationType type) { klass.setAnnotationType(type); } public AnnotationType getAnnotationType(Class klass) { return klass.getAnnotationType(); } public <E extends Enum<E>> E[] getEnumConstantsShared(Class<E> klass) { return klass.getEnumConstantsShared(); } public void blockedOn(Thread t, Interruptible b) { t.blockedOn(b); } }); } /* returns the class of the caller. */ static Class getCallerClass() { // NOTE use of more generic Reflection.getCallerClass() return Reflection.getCallerClass(3); } }