Back to index...

	/*
	* Copyright (c) 1994, 2013, 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.lang.reflect.Executable;
	import java.lang.annotation.Annotation;
	import java.security.AccessControlContext;
	import java.util.Properties;
	import java.util.PropertyPermission;
	import java.util.StringTokenizer;
	import java.util.Map;
	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.reflect.CallerSensitive;
	import sun.reflect.Reflection;
	import sun.security.util.SecurityConstants;
	import sun.reflect.annotation.AnnotationType;

	import jdk.internal.util.StaticProperty;

	/**
	* 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
	* @since JDK1.0
	*/
	public final class System {

	/* register the natives via the static initializer.
	*
	* VM will invoke the initializeSystemClass method to complete
	* the initialization for this class separated from clinit.
	* Note that to use properties set by the VM, see the constraints
	* described in the initializeSystemClass method.
	*/
	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 = null;

	/**
	* 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 = null;

	/**
	* 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 = null;

	/* 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<Object>() {
	public Object run() {
	s.getClass().getProtectionDomain().implies
	(SecurityConstants.ALL_PERMISSION);
	return null;
	}
	});
	}

	security = s;
	}

	/**
	* 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 running Java Virtual Machine's
	* high-resolution time source, 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 <i>origin</i> time (perhaps in the future, so values
	* may be negative). The same origin is used by all invocations of
	* this method in an instance of a Java virtual machine; other
	* virtual machine instances are likely to use a different origin.
	*
	* <p>This method provides nanosecond precision, but not necessarily
	* nanosecond resolution (that is, how frequently the value changes)
	* - no guarantees are made except that the resolution is at least as
	* good as that of {@link #currentTimeMillis()}.
	*
	* <p>Differences in successive calls that span greater than
	* approximately 292 years (2<sup>63</sup> nanoseconds) will not
	* correctly compute elapsed time due to numerical overflow.
	*
	* <p>The values returned by this method become meaningful only when
	* the difference between two such values, obtained within the same
	* instance of a Java virtual machine, is computed.
	*
	* <p> For example, to measure how long some code takes to execute:
	* <pre> {@code
	* long startTime = System.nanoTime();
	* // ... the code being measured ...
	* long estimatedTime = System.nanoTime() - startTime;}</pre>
	*
	* <p>To compare two nanoTime values
	* <pre> {@code
	* long t0 = System.nanoTime();
	* ...
	* long t1 = System.nanoTime();}</pre>
	*
	* one should use {@code t1 - t0 < 0}, not {@code t1 < t0},
	* because of the possibility of numerical overflow.
	*
	* @return the current value of the running Java Virtual Machine's
	* high-resolution time source, 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
	* <b>Deprecated.</b> <i>This property, and the mechanism
	* which implements it, may be removed in a future
	* release.</i> </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;
	}

	/**
	* Returns the system-dependent line separator string. It always
	* returns the same value - the initial value of the {@linkplain
	* #getProperty(String) system property} {@code line.separator}.
	*
	* <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
	* Windows systems it returns {@code "\r\n"}.
	*
	* @return the system-dependent line separator string
	* @since 1.7
	*/
	public static String lineSeparator() {
	return lineSeparator;
	}

	private static String lineSeparator;

	/**
	* 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>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.runFinalizersOnExit(value);
	}

	/**
	* Loads the native library specified by the filename argument. The filename
	* argument must be an absolute path name.
	*
	* 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 JNI Specification for more details.
	*
	* Otherwise, the filename argument is mapped to a native library image in
	* an implementation-dependent manner.
	*
	* <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 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.
	* @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)
	*/
	@CallerSensitive
	public static void load(String filename) {
	Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
	}

	/**
	* Loads the native library specified by the <code>libname</code>
	* argument. The <code>libname</code> argument must not contain any platform
	* specific prefix, file extension or path. If a native library
	* called <code>libname</code> is statically linked with the VM, then the
	* JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
	* See the JNI Specification 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>
	* 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 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.
	* @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)
	*/
	@CallerSensitive
	public static void loadLibrary(String libname) {
	Runtime.getRuntime().loadLibrary0(Reflection.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);

	/**
	* Create PrintStream for stdout/err based on encoding.
	*/
	private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
	if (enc != null) {
	try {
	return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
	} catch (UnsupportedEncodingException uee) {}
	}
	return new PrintStream(new BufferedOutputStream(fos, 128), true);
	}


	/**
	* Initialize the system class. Called after thread initialization.
	*/
	private static void initializeSystemClass() {

	// VM might invoke JNU_NewStringPlatform() to set those encoding
	// sensitive properties (user.home, user.name, boot.class.path, etc.)
	// during "props" initialization, in which it may need access, via
	// System.getProperty(), to the related system encoding property that
	// have been initialized (put into "props") at early stage of the
	// initialization. So make sure the "props" is available at the
	// very beginning of the initialization and all system properties to
	// be put into it directly.
	props = new Properties();
	initProperties(props); // initialized by the VM

	// There are certain system configurations that may be controlled by
	// VM options such as the maximum amount of direct memory and
	// Integer cache size used to support the object identity semantics
	// of autoboxing. Typically, the library will obtain these values
	// from the properties set by the VM. If the properties are for
	// internal implementation use only, these properties should be
	// removed from the system properties.
	//
	// See java.lang.Integer.IntegerCache and the
	// sun.misc.VM.saveAndRemoveProperties method for example.
	//
	// Save a private copy of the system properties object that
	// can only be accessed by the internal implementation. Remove
	// certain system properties that are not intended for public access.
	sun.misc.VM.saveAndRemoveProperties(props);


	lineSeparator = props.getProperty("line.separator");
	StaticProperty.jdkSerialFilter(); // Load StaticProperty to cache the property values
	sun.misc.Version.init();

	FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
	FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
	FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
	setIn0(new BufferedInputStream(fdIn));
	setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
	setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));

	// 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");

	// Setup Java signal handlers for HUP, TERM, and INT (where available).
	Terminator.setup();

	// 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();

	// 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);

	// register shared secrets
	setJavaLangAccess();

	// 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.
	// IMPORTANT: Ensure that this remains the last initialization action!
	sun.misc.VM.booted();
	}

	private static void setJavaLangAccess() {
	// 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 boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
	return klass.casAnnotationType(oldType, newType);
	}
	public AnnotationType getAnnotationType(Class<?> klass) {
	return klass.getAnnotationType();
	}
	public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
	return klass.getDeclaredAnnotationMap();
	}
	public byte[] getRawClassAnnotations(Class<?> klass) {
	return klass.getRawAnnotations();
	}
	public byte[] getRawClassTypeAnnotations(Class<?> klass) {
	return klass.getRawTypeAnnotations();
	}
	public byte[] getRawExecutableTypeAnnotations(Executable executable) {
	return Class.getExecutableTypeAnnotationBytes(executable);
	}
	public <E extends Enum<E>>
	E[] getEnumConstantsShared(Class<E> klass) {
	return klass.getEnumConstantsShared();
	}
	public void blockedOn(Thread t, Interruptible b) {
	t.blockedOn(b);
	}
	public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
	Shutdown.add(slot, registerShutdownInProgress, hook);
	}
	public int getStackTraceDepth(Throwable t) {
	return t.getStackTraceDepth();
	}
	public StackTraceElement getStackTraceElement(Throwable t, int i) {
	return t.getStackTraceElement(i);
	}
	public String newStringUnsafe(char[] chars) {
	return new String(chars, true);
	}
	public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
	return new Thread(target, acc);
	}
	public void invokeFinalize(Object o) throws Throwable {
	o.finalize();
	}
	});
	}
	}

Back to index...