System class

System class contains system-level useful class fields and methods. System class cannot be instantiated.

Standard Stream

static PrintStream err
The "standard" error output stream.
static InputStream in
The "standard" input stream.
static PrintStream out
The "standard" output stream.
static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)
Copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.
static String clearProperty(String key)
Removes the system property.
static Console console()
Returns the Console object.
static long currentTimeMillis()
Returns the current time in milliseconds.
static void exit(int status)
Terminates the Java Virtual Machine.
static void gc()
Runs the garbage collector.
static String getenv(String name)
Gets the value of the environment variable.
static Map<String,String> getenv()
Returns an string map of the system environment.
static Properties getProperties()
Determines the current system properties.
static String getProperty(String key)
Gets the system property indicated.
static String getProperty(String key, String def)
Gets the system property.
static int identityHashCode(Object x)
Returns the same hash code for the given object as would be returned by the default method hashCode().
static Channel inheritedChannel()
Returns the channel inherited from the entity that created this Java virtual machine.
static void load(String filename)
Loads a code file with the filename as a dynamic library.
static void loadLibrary(String libname)
Loads the system library by the libname argument.
static String mapLibraryName(String libname)
Maps a library name into a platform-specific string.
static long nanoTime()
Returns the current system time in nanoseconds.
static SecurityManager getSecurityManager()
Gets the system security interface.
static void setSecurityManager(SecurityManager s)
Sets the System security.
static void runFinalization()
Runs the finalization methods of any objects pending finalization.
static void setProperties(Properties props)
Sets the system properties to the Properties argument.
static String setProperty(String key, String value)
Sets the system property.
static void setErr(PrintStream err)
Reassigns the "standard" error output stream.
static void setIn(InputStream in)
Reassigns the "standard" input stream.
static void setOut(PrintStream out)
Reassigns the "standard" output stream.
  Java Book 
    Essential Classes  

  1. System class
  2. Standard Stream
  3. Copy array
  4. Get/set system property
  5. Get the system environment
  6. Current system time