Android - An Open Handset Alliance Project

java.lang
public final class

java.lang.System

java.lang.Object
	java.lang.System

Class System provides a standard place for programs to find system related information. All System API is static.

Summary

Constants


PrintStream	err	Default error output stream
InputStream	in	Default input stream
PrintStream	out	Default output stream

Public Methods

static	void	arraycopy(Object array1, int start1, Object array2, int start2, int length)
		Copies the contents of `array1` starting at offset `start1` into `array2` starting at offset `start2` for `length` elements.
static	String	clearProperty(String key)
		Removes the system property for the specified key.
static	long	currentTimeMillis()
		Answers the current time expressed as milliseconds since the time 00:00:00 UTC on January 1, 1970.
static	void	exit(int code)
		Causes the virtual machine to stop running, and the program to exit.
static	void	gc()
		Indicate to the virtual machine that it would be a good time to collect available memory.
static	Properties	getProperties()
		Answers the system properties.
static	String	getProperty(String prop, String defaultValue)
		Answers the value of a particular system property.
static	String	getProperty(String prop)
		Answers the value of a particular system property.
static	SecurityManager	getSecurityManager()
		Answers the active security manager.
static	String	getenv(String var)
		Returns an environment variable.
static	Map	getenv()
		Returns all environment variables.
static	int	identityHashCode(Object anObject)
		Answers an integer hash code for the parameter.
static	Channel	inheritedChannel()
		Returns the inherited channel from the system-wide provider.
static	void	load(String pathName)
		Loads the specified file as a dynamic library.
static	void	loadLibrary(String libName)
		Loads and links the library specified by the argument.
static	String	mapLibraryName(String userLibName)
		Answers the platform specific file name format for the shared library named by the argument.
static	long	nanoTime()
		Returns the most precise time measurement in nanoseconds that's available.
static	void	runFinalization()
		Provides a hint to the virtual machine that it would be useful to attempt to perform any outstanding object finalizations.
static	void	runFinalizersOnExit(boolean flag)
		This method is deprecated. This method is unsafe.
static	void	setErr(PrintStream newErr)
		Sets the value of the static slot "err" in the receiver to the passed in argument.
static	void	setIn(InputStream newIn)
		Sets the value of the static slot "in" in the receiver to the passed in argument.
static	void	setOut(PrintStream newOut)
		Sets the value of the static slot "out" in the receiver to the passed in argument.
static	void	setProperties(Properties p)
		Answers the system properties.
static	String	setProperty(String prop, String value)
		Sets the value of a particular system property.
static	void	setSecurityManager(SecurityManager sm)
		Sets the active security manager.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

	Object	clone()
		Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
	boolean	equals(Object o)
		Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
	void	finalize()
		Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
final	Class	getClass()
		Answers the unique instance of java.lang.Class which represents the class of the receiver.
	int	hashCode()
		Answers an integer hash code for the receiver.
final	void	notify()
		Causes one thread which is `wait` ing on the receiver to be made ready to run.
final	void	notifyAll()
		Causes all threads which are `wait` ing on the receiver to be made ready to run.
	String	toString()
		Answers a string containing a concise, human-readable description of the receiver.
final	void	wait(long time, int frac)
		Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by `notify` or `notifyAll`) or the expiration of the timeout.
final	void	wait(long time)
		Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by `notify` or `notifyAll`) or the expiration of the timeout.
final	void	wait()
		Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by `notify` or `notifyAll`).

Details

Constants

public static final PrintStream err

Default error output stream

public static final InputStream in

Default input stream

public static final PrintStream out

Default output stream

Public Methods

public static void arraycopy(Object array1, int start1, Object array2, int start2, int length)

Copies the contents of array1 starting at offset start1 into array2 starting at offset start2 for length elements.

Parameters

array1	the array to copy out of
start1	the starting index in array1
array2	the array to copy into
start2	the starting index in array2
length	the number of elements in the array to copy

public static String clearProperty(String key)

Removes the system property for the specified key.

Please see the Java SE API documentation for further information on this method.

Parameters

key	the system property to be removed.

Returns

previous value or null if no value existed

Throws

NullPointerException	if the `key` argument is `null`.
IllegalArgumentException	if the `key` argument is empty.
SecurityException	if a security manager exists and write access to the specified property is not allowed.

public static long currentTimeMillis()

Answers the current time expressed as milliseconds since the time 00:00:00 UTC on January 1, 1970.

Returns

the time in milliseconds.

public static void exit(int code)

Causes the virtual machine to stop running, and the program to exit. If runFinalizersOnExit(true) has been invoked, then all finalizers will be run first.

Parameters

code	the return code.

Throws

SecurityException	if the running thread is not allowed to cause the vm to exit.

public static void gc()

Indicate to the virtual machine that it would be a good time to collect available memory. Note that, this is a hint only.

public static Properties getProperties()

Answers the system properties. Note that this is not a copy, so that changes made to the returned Properties object will be reflected in subsequent calls to getProperty and getProperties.

Security managers should restrict access to this API if possible.

Returns

the system properties

public static String getProperty(String prop, String defaultValue)

Answers the value of a particular system property. If no such property is found, answers the defaultValue.

Parameters

prop	the system property to look up
defaultValue	return value if system property is not found

Returns

the value of the specified system property, or defaultValue if the property doesn't exist

public static String getProperty(String prop)

Answers the value of a particular system property. Answers null if no such property exists,

The properties currently provided by the virtual machine are:

        java.vendor.url
        java.class.path
        user.home
        java.class.version
        os.version
        java.vendor
        user.dir
        user.timezone
        path.separator
        os.name
        os.arch
        line.separator
        file.separator
        user.name
        java.version
        java.home

Parameters

prop	the system property to look up

Returns

the value of the specified system property, or null if the property doesn't exist

public static SecurityManager getSecurityManager()

Answers the active security manager.

Returns

the system security manager object.

public static String getenv(String var)

Returns an environment variable.

Parameters

var	the name of the environment variable

Returns

the value of the specified environment variable

public static Map getenv()

Returns all environment variables.

Returns

A Map of all environment variables.

public static int identityHashCode(Object anObject)

Answers an integer hash code for the parameter. The hash code returned is the same one that would be returned by java.lang.Object.hashCode(), whether or not the object's class has overridden hashCode(). The hash code for null is 0.

Parameters

anObject	the object

Returns

the hash code for the object

public static Channel inheritedChannel()

Returns the inherited channel from the system-wide provider.

Returns

A Channel or null.

Throws

	IOException
IOException

public static void load(String pathName)

Loads the specified file as a dynamic library.

Parameters

pathName	the path of the file to be loaded

public static void loadLibrary(String libName)

Loads and links the library specified by the argument.

Parameters

libName	the name of the library to load

Throws

UnsatisfiedLinkError	if the library could not be loaded
SecurityException	if the library was not allowed to be loaded

public static String mapLibraryName(String userLibName)

Answers the platform specific file name format for the shared library named by the argument.

Parameters

userLibName	the name of the library to look up.

Returns

the platform specific filename for the library

public static long nanoTime()

Returns the most precise time measurement in nanoseconds that's available.

Returns

The current time in nanoseconds.

public static void runFinalization()

Provides a hint to the virtual machine that it would be useful to attempt to perform any outstanding object finalizations.

public static void runFinalizersOnExit(boolean flag)

This method is deprecated. This method is unsafe.

Ensure that, when the virtual machine is about to exit, all objects are finalized. Note that all finalization which occurs when the system is exiting is performed after all running threads have been terminated.

Parameters

flag	true means finalize all on exit.

public static void setErr(PrintStream newErr)

Sets the value of the static slot "err" in the receiver to the passed in argument.

Parameters

newErr	the new value for err.

public static void setIn(InputStream newIn)

Sets the value of the static slot "in" in the receiver to the passed in argument.

Parameters

newIn	the new value for in.

public static void setOut(PrintStream newOut)

Sets the value of the static slot "out" in the receiver to the passed in argument.

Parameters

newOut	the new value for out.

public static void setProperties(Properties p)

Answers the system properties. Note that the object which is passed in not copied, so that subsequent changes made to the object will be reflected in calls to getProperty and getProperties.

Security managers should restrict access to this API if possible.

Parameters

p	the property to set

public static String setProperty(String prop, String value)

Sets the value of a particular system property.

Parameters

prop	the system property to change
value	the value to associate with prop

Returns

the old value of the property, or null

public static void setSecurityManager(SecurityManager sm)

Sets the active security manager. Note that once the security manager has been set, it can not be changed. Attempts to do so will cause a security exception.

Parameters

sm	the new security manager

Throws

SecurityException	if the security manager has already been set and if its checkPermission method does not allow to redefine the security manager.


e.g. "intent" or "activity"

Android - An Open Handset Alliance Project

Documentation

Goodies

java.lang.System

Summary

Constants

Public Methods

Methods inherited from class java.lang.Object

Details

Constants

public static final PrintStream err

public static final InputStream in

public static final PrintStream out

Public Methods

public static void arraycopy(Object array1, int start1, Object array2, int start2, int length)

Parameters

public static String clearProperty(String key)

Parameters

Returns

Throws

public static long currentTimeMillis()

Returns

public static void exit(int code)

Parameters

Throws

See Also

public static void gc()

public static Properties getProperties()

Returns

public static String getProperty(String prop, String defaultValue)

Parameters

Returns

public static String getProperty(String prop)

Parameters

Returns

public static SecurityManager getSecurityManager()

Returns

public static String getenv(String var)

Parameters

Returns

public static Map getenv()

Returns

public static int identityHashCode(Object anObject)

Parameters

Returns

See Also

public static Channel inheritedChannel()

Returns

Throws

See Also

public static void load(String pathName)

Parameters

public static void loadLibrary(String libName)

Parameters

Throws

public static String mapLibraryName(String userLibName)

Parameters

Returns

public static long nanoTime()

Returns

public static void runFinalization()

public static void runFinalizersOnExit(boolean flag)

Parameters

public static void setErr(PrintStream newErr)

Parameters

public static void setIn(InputStream newIn)

Parameters

public static void setOut(PrintStream newOut)

Parameters

public static void setProperties(Properties p)

Parameters

public static String setProperty(String prop, String value)

Parameters

Returns

public static void setSecurityManager(SecurityManager sm)

Parameters

Throws