Android
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

      Value  
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()
Returns 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()
Returns the system properties.
      static    String  getProperty(String prop, String defaultValue)
Returns the value of a particular system property.
      static    String  getProperty(String prop)
Returns the value of a particular system property.
      static    SecurityManager  getSecurityManager()
Returns the active security manager.
      static    String  getenv(String var)
Returns an environment variable.
      static    Map<StringString getenv()

Returns all environment variables.

      static    int  identityHashCode(Object anObject)
Returns 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)
Returns 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)
Returns 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

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()

Returns 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.

See Also

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()

Returns 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)

Returns the value of a particular system property. If no such property is found, returns 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)

Returns the value of a particular system property. Returns 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()

Returns 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<StringString> getenv()

Returns all environment variables.

Returns

  • A Map of all environment variables.

public static int identityHashCode(Object anObject)

Returns 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

See Also

public static Channel inheritedChannel()

Returns the inherited channel from the system-wide provider.

Returns

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)

Returns 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)

Returns 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.
Copyright 2007 Google Inc. Build 0.9_r1-98467 - 14 Aug 2008 18:56