java.lang
Class System

java.lang.Object
  java.lang.System

public final class System
extends Object

System represents system-wide resources; things that represent the general environment. As such, all methods are static.

Since:

1.0

Field Summary

static PrintStream	err
static PrintStream	out

Method Summary

static void	arraycopy(Object src, int srcStart, Object dest, int destStart, int len) Copy one array onto another from src[srcStart] ...
static long	currentTimeMillis() Get the current time, measured in the number of milliseconds from the beginning of Jan.
static void	exit(int status) Terminate the Virtual Machine.
static String	getProperty(String key) Get a single system property by name.
static String	getProperty(String key, String def) Get a single system property by name.
static int	identityHashCode(Object o) Get a hash code computed by the VM for the Object.

Methods inherited from class java.lang.Object

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

Field Detail

out

public static final PrintStream out

err

public static final PrintStream err

Method Detail

currentTimeMillis

public static long currentTimeMillis()

Get the current time, measured in the number of milliseconds from the beginning of Jan. 1, 1970. This is gathered from the system clock, with any attendant incorrectness (it may be timezone dependent).

Returns:

the current time

See Also:

Date

arraycopy

public static void arraycopy(Object src,
                             int srcStart,
                             Object dest,
                             int destStart,
                             int len)

Copy one array onto another from src[srcStart] ... src[srcStart+len-1] to dest[destStart] ... dest[destStart+len-1]. First, the arguments are validated: neither array may be null, they must be of compatible types, and the start and length must fit within both arrays. Then the copying starts, and proceeds through increasing slots. If src and dest are the same array, this will appear to copy the data to a temporary location first. An ArrayStoreException in the middle of copying will leave earlier elements copied, but later elements unchanged.

Parameters:

src - the array to copy elements from

srcStart - the starting position in src

dest - the array to copy elements to

destStart - the starting position in dest

len - the number of elements to copy

Throws:

NullPointerException - if src or dest is null

ArrayStoreException - if src or dest is not an array, if they are not compatible array types, or if an incompatible runtime type is stored in dest

IndexOutOfBoundsException - if len is negative, or if the start or end copy position in either array is out of bounds

identityHashCode

public static int identityHashCode(Object o)

Get a hash code computed by the VM for the Object. This hash code will be the same as Object's hashCode() method. It is usually some convolution of the pointer to the Object internal to the VM. It follows standard hash code rules, in that it will remain the same for a given Object for the lifetime of that Object.

Parameters:

o - the Object to get the hash code for

Returns:

the VM-dependent hash code for this Object

Since:

1.1

getProperty

public static String getProperty(String key)

Get a single system property by name. A security check may be performed, checkPropertyAccess(key).

Parameters:

key - the name of the system property to get

Returns:

the property, or null if not found

Throws:

java.lang.SecurityException - if permission is denied

NullPointerException - if key is null

IllegalArgumentException - if key is ""

getProperty

public static String getProperty(String key,
                                 String def)

Get a single system property by name. A security check may be performed, checkPropertyAccess(key).

Parameters:

key - the name of the system property to get

def - the default

Returns:

the property, or def if not found

Throws:

java.lang.SecurityException - if permission is denied

NullPointerException - if key is null

IllegalArgumentException - if key is ""

exit

public static void exit(int status)

Terminate the Virtual Machine. This just calls Runtime.getRuntime().exit(status), and never returns. Obviously, a security check is in order, checkExit.

Parameters:

status - the exit status; by convention non-zero is abnormal

Throws:

java.lang.SecurityException - if permission is denied

See Also:

Runtime.exit(int)