java.lang
Class System

java.lang.Object
  java.lang.System

public final class System
extends Object

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

Among the facilities provided by the System class are standard input, standard output, and error output streams; access to externally defined "properties"; a means of loading files and libraries; and a utility method for quickly copying a portion of an array.

Since:

JDK1.0

Version:

1.125, 12/03/01

Author:

Arthur van Hoff, Helge Böhme (JControl)

Available on JControl Devices:

lib

Field Summary

static ConsoleOutputStream	err The "standard" error output stream.
static ConsoleInputStream	in The "standard" input stream.
static ConsoleOutputStream	out The "standard" output stream.

Constructor Summary

System()

Method Summary

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 void	setErr(ConsoleOutputStream newErr) Reassigns the "standard" error output stream.
static void	setIn(ConsoleInputStream newIn) Reassigns the "standard" input stream.
static void	setOut(ConsoleOutputStream newOut) Reassigns the "standard" output stream.

Methods inherited from class java.lang.Object

clone, equals, notifyAll, wait

Field Detail

err

public static ConsoleOutputStream err

The "standard" error output stream. This stream is already open and ready to accept output data.

Typically this stream corresponds to display output or another output destination specified by the host environment or user. By convention, this output stream is used to display error messages or other information that should come to the immediate attention of a user even if the principal output stream, the value of the variable out, has been redirected to a file or other destination that is typically not continuously monitored.

See Also:

ConsoleOutputStream

in

public static ConsoleInputStream in

The "standard" input stream. This stream is already open and ready to supply input data. Typically this stream corresponds to keyboard input or another input source specified by the host environment or user.

See Also:

ConsoleInputStream

out

public static ConsoleOutputStream out

The "standard" output stream. This stream is already open and ready to accept output data. Typically this stream corresponds to display output or another output destination specified by the host environment or user.

For simple stand-alone Java applications, a typical way to write a line of output data is:

     System.out.println(data)
 

See the println methods in class PrintStream.

See Also:

ConsoleOutputStream

Constructor Detail

System

public System()

Method Detail

arraycopy

public 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. A subsequence of array components are copied from the source array referenced by src to the destination array referenced by dest. The number of components copied is equal to the length argument. The components at positions srcPos through srcPos+length-1 in the source array are copied into positions destPos through destPos+length-1, respectively, of the destination array.

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

If dest 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:

• The src argument refers to an object that is not an array.
• The dest argument refers to an object that is not an array.
• The src argument and dest argument refer to arrays whose component types are different primitive types.
• The src argument refers to an array with a primitive component type and the dest argument refers to an array with a reference component type.
• The src argument refers to an array with a reference component type and the dest argument refers to an array with a primitive component type.

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

• The srcPos argument is negative.
• The destPos argument is negative.
• The length argument is negative.
• srcPos+length is greater than src.length, the length of the source array.
• destPos+length is greater than dest.length, the length of the destination array.

Otherwise, if any actual component of the source array from position srcPos through srcPos+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[srcPos+k] cannot be converted to the component type of the destination array; when the exception is thrown, source array components from positions srcPos through srcPos+k-1 will already have been copied to destination array positions destPos through destPos+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.)

A wrapper for Management.arraycopy(Object src, int srcPos, Object dest, int destPos, int length).

Parameters:

src - the source array.

srcPos - starting position in the source array.

dest - the destination array.

destPos - starting position in the destination data.

length - the number of array elements to be copied.

Throws:

java.lang.IndexOutOfBoundsException - if copying would cause access of data outside array bounds.

java.lang.ArrayStoreException - if an element in the src array could not be stored into the dest array because of a type mismatch.

java.lang.NullPointerException - if either src or dest is null.

setErr

public static void setErr(ConsoleOutputStream newErr)

Reassigns the "standard" error output stream.

First, if there is a security manager, its checkPermission method is called with a RuntimePermission("setIO") permission to see if it's ok to reassign the "standard" error output stream.

Parameters:

newErr - the new standard error output stream.

Throws:

java.lang.SecurityException - if a security manager exists and its checkPermission method doesn't allow reassigning of the standard error output stream.

Since:

JDK1.1

See Also:

SecurityManager.checkPermission(java.security.Permission), RuntimePermission

setIn

public static void setIn(ConsoleInputStream newIn)

Reassigns the "standard" input stream.

First, if there is a security manager, its checkPermission method is called with a RuntimePermission("setIO") permission to see if it's ok to reassign the "standard" input stream.

Parameters:

newIn - the new standard input stream.

Throws:

java.lang.SecurityException - if a security manager exists and its checkPermission method doesn't allow reassigning of the standard input stream.

Since:

JDK1.1

See Also:

SecurityManager.checkPermission(java.security.Permission), RuntimePermission

setOut

public static void setOut(ConsoleOutputStream newOut)

Reassigns the "standard" output stream.

First, if there is a security manager, its checkPermission method is called with a RuntimePermission("setIO") permission to see if it's ok to reassign the "standard" output stream.

Parameters:

newOut - the new standard output stream

Throws:

java.lang.SecurityException - if a security manager exists and its checkPermission method doesn't allow reassigning of the standard output stream.

Since:

JDK1.1

See Also:

SecurityManager.checkPermission(java.security.Permission), RuntimePermission