java.lang
Class System

java.lang.Object
  extended by java.lang.System

public final class System
extends Object

The System class contains several useful class fields and methods. It cannot be instantiated.

Since:
JDK1.0, CLDC 1.0
Version:
1/1/08 (CLDC 1.1)

Field Summary
static PrintStream err
          The "standard" error output stream.
static PrintStream out
          The "standard" output stream.
 
Method Summary
static void arraycopy(Object src, int srcOffset, Object dst, int dstOffset, int len)
          Copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.
static long currentTimeMillis()
          Returns the current time in milliseconds.
static void exit(int code)
          Terminates the currently running Java VM and reboots the mote.
static void gc()
          Runs the garbage collector.
static String getProperty(String key)
          Gets the system property indicated by the specified key.
static int identityHashCode(Object x)
          Returns the same hashcode for the given object as would be returned by the default method hashCode(), whether or not the given object's class overrides hashCode().
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

out

public static final PrintStream out
The "standard" output stream. This stream is already open and ready to accept output data.

For Sentilla motes, output requires the mote to be connected to a special host framework. Normally output is thrown away.


err

public static final PrintStream err
The "standard" error output stream. This stream is already open and ready to accept output data.

For Sentilla motes, output requires the mote to be connected to a special host framework. Normally output is thrown away.

Method Detail

arraycopy

public static void arraycopy(Object src,
                             int srcOffset,
                             Object dst,
                             int dstOffset,
                             int len)
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 src to the destination array referenced by dst. The number of components copied is equal to the length argument. The components at positions srcOffset through srcOffset+length-1 in the source array are copied into positions dstOffset through dstOffset+length-1, respectively, of the destination array.

If the src and dst arguments refer to the same array object, then the copying is performed as if the components at positions srcOffset through srcOffset+length-1 were first copied to a temporary array with length components and then the contents of the temporary array were copied into positions dstOffset through dstOffset+length-1 of the destination array.

If dst is null, then a NullPointerException is thrown.

If src is null, then a NullPointerException is thrown and the destination array is not modified.

Otherwise, if any of the following is true, an ArrayStoreException is thrown and the destination is not modified:

Otherwise, if any of the following is true, an IndexOutOfBoundsException is thrown and the destination is not modified:

Otherwise, if any actual component of the source array from position srcOffset through srcOffset+length-1 cannot be converted to the component type of the destination array by assignment conversion, an ArrayStoreException is thrown. In this case, let k be the smallest nonnegative integer less than length such that src[srcOffset+k] cannot be converted to the component type of the destination array; when the exception is thrown, source array components from positions srcOffset through srcOffset+k-1 will already have been copied to destination array positions dstOffset through dstOffset+k-1 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.)

Parameters:
src - the source array.
srcOffset - start position in the source array.
dst - the destination array.
dstOffset - start position in the destination data.
len - the number of array elements to be copied.
Throws:
IndexOutOfBoundsException - if copying would cause access of data outside array bounds.
ArrayStoreException - if an element in the src array could not be stored into the dest array because of a type mismatch.
NullPointerException - if either src or dst is null.

exit

public static void exit(int code)
Terminates the currently running Java VM and reboots the mote. The statusargument is ignored.

Parameters:
code - ignored

currentTimeMillis

public static long currentTimeMillis()
Returns the current time in milliseconds.

Returns:
the time, measured in milliseconds, since the mote rebooted.

gc

public static void gc()
Runs the garbage collector.

Calling the gc 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.

The call System.gc() is effectively equivalent to the call:

 Runtime.getRuntime().gc()
 

See Also:
Runtime.gc()

getProperty

public static String getProperty(String key)
Gets the system property indicated by the specified key.

Parameters:
key - the name of the system property.
Returns:
the string value of the system property, or null if there is no property with that key.
Throws:
NullPointerException - if key is null.
IllegalArgumentException - if key is empty.

identityHashCode

public static int identityHashCode(Object x)
Returns the same hashcode for the given object as would be returned by the default method hashCode(), whether or not the given object's class overrides hashCode(). The hashcode for the null reference is zero.

Parameters:
x - object for which the hashCode is to be calculated
Returns:
the hashCode
Since:
JDK1.1


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