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java.lang.Object
 java.lang.System
- See Also:
- Top Examples, Source Code
public static void arraycopy(Object src,
int srcPos,
Object dest,
int destPos,
int length)- See Also:
- NullPointerException, ArrayStoreException, IndexOutOfBoundsException
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- Description Add your codes or notes Search More Java Examples
[655]Copy Byte Array
By Anonymous on 2005/07/27 14:09:53 Rate
private byte [ ] copyByteArray ( byte [ ] source ) {
byte [ ] dest = new byte [ source.length ] ;
System.arraycopy ( source, 0, dest, 0, source.length ) ;
return dest;
}
[1888]Copying an array fast
By Anonymous on 2007/06/10 07:14:18 Rate
Although copying an array isn't particularly difficult, it is an operation which benefits from a native implementation. Therefore java.lang.System includes a static System.arraycopy ( ) method you can use to copy one array to another.
public static void arraycopy ( Object source, int sourcePosition,
Object destination, int destinationPosition, int numberOfElements )
System.arraycopy ( ) copies numberOfElements elements from the array source, beginning with the element at sourcePosition, to the array destination starting at destinationPosition. The destination array must already exist when System.arraycopy ( ) is called. The method does not create it. The source and destination arrays must be of the same type.
For example,
int [ ] unicode = new int [ 65536 ] ;
for ( int i = 0; i < unicode.length; i++ ) {
unicode [ i ] = i;
}
int [ ] latin1 = new int [ 256 ] ;
System.arraycopy ( unicode, 0, latin1, 0, 256 ) ;
public static String clearProperty(String key) - See Also:
SecurityManager.checkPropertiesAccess(), SecurityException, Properties, setProperty(java.lang.String, java.lang.String), getProperty(java.lang.String), IllegalArgumentException, NullPointerException
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public static long currentTimeMillis() - See Also:
Date
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[147]Timing
By Anonymous on 2005/05/24 10:00:01 Rate
public static void main ( String [ ] args )
{
// JIT/hotspot warmup:
for ( int r = 0; r < 3000; ++ r ) System.currentTimeMillis ( ) ;
long time = System.currentTimeMillis ( ) , time_prev = time;
for ( int i = 0; i < 5; ++ i )
{
// Busy wait until system time changes:
while ( time == time_prev )
time = System.currentTimeMillis ( ) ;
System.out.println ( "delta = " + ( time - time_prev ) + " ms" ) ;
time_prev = time;
}
}
public static final PrintStream err - Geek's Notes:
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[159]Additional debugging output
By Anonymous on 2003/01/30 09:38:33 Rate
//some additional debugging output:
Thread.dumpStack ( ) ;
System.err.println ( this ) ;
System.err.println ( Thread.currentThread ( ) ) ;
[1801]function to exit program, in case of an error:
By ab on 2006/08/06 19:29:43 Rate
// function to exit program, in case of an error:
public static void die ( String s ) {
System.err.println ( "Error: ", s ) ;
System.exit ( 1 ) ;
}
public static void exit(int status) - See Also:
- SecurityException
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public static void gc() - Geek's Notes:
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[1541]Purpose of garbage collection
By Anonymous on 2005/09/22 15:29:53 Rate
This method only request garbage collection, you can not force GC. JVM does not guarantee that GC will be started immediately[1670]_
By Anonymous on 2005/11/04 20:23:08 Rate
The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused. A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.
public static Map<String,String> getenv() - See Also:
ProcessBuilder.environment(), getenv(String), checkPermission, SecurityException, RuntimePermission, Object.hashCode(), Object.equals(java.lang.Object), ClassCastException, NullPointerException
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public static String getenv(String name) - See Also:
SecurityException, RuntimePermission, checkPermission
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public static Properties getProperties() - See Also:
-
SecurityManager.checkPropertiesAccess(), SecurityException, setProperties(java.util.Properties), getProperty(String)
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- Description Add your codes or notes Search More Java Examples
[1706]Reading System Properties to a file
By Mohammed Zabin (mszabin { at } yahoo { dot } com) on 2006/02/06 00:31:45 Rate
This code gets system properties and store them to an exteranl file
input/output streams.
===================================================================
import java.util.*;
import java.io.*;
public class SystemTest {
public static void main ( String [ ] args ) {
//Current Time Milliseconds
System.out.println ( System.currentTimeMillis ( ) ) ;
System.out.println ( System.getenv ( "Foo" ) ) ;
// The Following code writes system properties
// to a specific file, using PrintStream and File
// classes
// Instantiate a property object
Properties prp = new Properties ( ) ;
//Use System class to fill the property object with its values
prp = System.getProperties ( ) ;
//Instantiate a PrintStream instance that takes a file
// instance as a paramter to write system properties
// to it.
try {
prp.list ( new PrintStream ( new File ( "D:\\Debug.txt" ) ) ) ;
} catch ( IOException ioe ) {
System.out.println ( ioe.toString ( ) ) ;
}
}
}
[1930]Print out all the System Properties
By Anonymous on 2007/08/16 18:36:24 Rate
Properties sysProps = System.getProperties ( ) ;
Enumeration en = sysProps.keys ( ) ;
while ( en.hasMoreElements ( ) )
{
//add the key=value pairs
Object keyObj = en.nextElement ( ) ;
String key = ( String ) keyObj;
Object valueObj = sysProps.getProperty ( key ) ;
System.out.println ( key + " : " + valueObj.toString ( ) ) ;
}
public static String getProperty(String key) - See Also:
getProperties(), SecurityManager.checkPropertyAccess(java.lang.String), SecurityException, setProperty(java.lang.String, java.lang.String), IllegalArgumentException, NullPointerException
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[305]Get system property
By Anonymous on 2003/10/27 03:58:05 Rate
System.getProperty ( "file.separator" ) ;[563]_
By Anonymous on 2003/12/10 17:01:42 Rate
String vers = System.getProperty ( "java.version" ) ;
if ( vers.compareTo ( "1.4.1" ) < 0 ) {
System.out.println ( "!!!WARNING: This program must be run with a 1.4.1 or higher version VM!!!" ) ;
System.exit ( 1 ) ;
} [1758]Default timeouts properties in JDK 1.4
By Anonymous on 2006/05/23 11:36:33 Rate
In the 1.4 JDK, Sun has documented a pair of system properties that allow you to modify the default timeouts used by sockets. These two properties are sun.net.client.defaultConnectTimeout and sun.net.client.defaultReadTimeout, and both specify timeout values in milliseconds.
System.setProperty ( "sun.net.client.defaultConnectTimeout", "30000" ) ;
System.setProperty ( "sun.net.client.defaultReadTimeout", "30000" ) ;[1955]Find Current Temp Directory
By Anonymous on 2008/02/22 08:30:58 Rate
We are using getProperty ( String key ) method to find the current temp directory. The getProperty ( String key ) is defined into System class. System class extends directly Object class. System class is defined final so any class never extends System class. System class allow us to get or set system information. In this example we are pasing "java.io.tmpdir" as key to get the current temp directory into getProperty ( ) method.
public class TempDirExample
{
public static void main ( String [ ] args )
{
System.out.println ( "OS current temporary directory is "
+ System.getProperty ( "java.io.tmpdir" ) ) ;
}
} [1956]java.io.tmpdir Inconsitency
By Anonymous on 2008/02/22 08:36:19 Rate
Java has a way of giving you the path to the temp directory in a platform neutral way. You simply ask the system for the ???java.io.tmpdir??? property and you???re good to go. Here???s an example of code that does that and prints the result.
The Code
package tmp;
public class TempDir {
public static void main ( String [ ] args ) {
String tmpDir = System.getProperty ( "java.io.tmpdir" ) ;
System.out.println ( "java.io.tmpdir: [ " + tmpDir + " ] " ) ;
}
}
The Output
On Windows: java.io.tmpdir: [ C:\DOCUME~1\joshua\LOCALS~1\Temp\ ]
On Solaris: java.io.tmpdir: [ /var/tmp/ ]
On Linux: java.io.tmpdir: [ /tmp ]
On Mac OS X: java.io.tmpdir: [ /tmp ]
As you can see, it gives you the temp directory that is appropriate to the platform. Now you just use it. Well, almost. Take a look at those paths again. The Linux and Mac OS X ones vary slightly from the others. Not much, but just enough to cause your application to fail if you don???t take precautions. You see it? Yep, the Linux and Mac OS X output don???t end in the file separator ( forward slash ) ! So when you build paths using code like the following???
String myPath = System.getProperty ( "java.io.tmpdir" ) + "some"
+ File.separator + "place" + File.separator + "somefile.txt" ) ;
???they fail.
On Windows:C:\DOCUME~1\joshua\LOCALS~1\Temp\some\place\somefile.txt
On Solaris: /var/tmp/some/place/somefile.txt
On Linux: /tmpsome/place/somefile.txt
On Mac OS X: /tmpsome/place/somefile.txt
tmp and some get slammed together on Linux and Mac OS X as tmpsome without the file separator between them. This means that if you want to use the java.io.tmpdir property to build a path, you have to check for the file separator at the end of the String and add it if it???s not there.
The other option is just to add the File.separator no matter what when building paths with java.io.tmpdir. In limited tests on Windows, Solaris, Linux and Mac OS X it looks like the operating system handles doubled file separators without problems. It simply swallows the second one and acts as if it was a single file separator.[1992]file paths with/without file sep
By pstanton on 2009/04/07 19:54:30 Rate
if you're using a file path and you don't know if it ends with a slash,
the easiest way to handle that is to create files using
new File ( someunknownpath, "filename.txt" ) ;
that way, if someunknownpath does or doesn't end with a file sep it
will be handled correctly every time.
if you just want to get a path and not a file object use
new File ( someunknownpath, "filename.txt" ) .getAbsolutePath ( ) ;
the overhead should be minimal.
public static String getProperty(String key,
String def)- See Also:
getProperties(), SecurityManager.checkPropertyAccess(java.lang.String), setProperty(java.lang.String, java.lang.String), IllegalArgumentException, NullPointerException, SecurityException
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[1935]Setting the Value of a System Property
By Anonymous on 2007/10/30 17:32:22 Rate
// Get a system property
String dir = System.getProperty ( "user.dir" ) ;
// Set a system property
String previousValue = System.setProperty ( "application.property", "newValue" ) ;
public static SecurityManager getSecurityManager() - See Also:
setSecurityManager(java.lang.SecurityManager)
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public static int identityHashCode(Object x) - Geek's Notes:
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public static final InputStream in - Geek's Notes:
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[1158]Read input from keyboard
By Anonymous on 2005/04/25 11:33:25 Rate
int rows = 0, cols = 0;
String tmp;
System.out.print ( name + ": how many rows? " ) ;
tmp = ( new BufferedReader ( new InputStreamReader ( System.in ) ) ) .readLine ( ) ;
rows = Integer.parseInt ( tmp ) ;
System.out.print ( name + ": how many cols? " ) ;
tmp = ( new BufferedReader ( new InputStreamReader ( System.in ) ) ) .readLine ( ) ;
cols = Integer.parseInt ( tmp ) ;
String [ ] [ ] strTable = new String [ rows ] [ cols ] ;
[1802]read a line from STDIN (=System.in)
By ab on 2006/08/06 19:35:21 Rate
// read a line from STDIN ( =System.in )
BufferedReader in = new BufferedReader ( new InputStreamReader ( System.in ) ) ;
String line;
line=in.readLine ( ) ;
public static Channel inheritedChannel()
throws IOException- See Also:
- SecurityException,
SelectorProvider
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public static void load(String filename) - See Also:
SecurityManager.checkLink(java.lang.String), NullPointerException, UnsatisfiedLinkError, SecurityException
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public static void loadLibrary(String libname) - See Also:
SecurityManager.checkLink(java.lang.String), NullPointerException, UnsatisfiedLinkError, SecurityException
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public static String mapLibraryName(String libname) - See Also:
ClassLoader.findLibrary(java.lang.String), loadLibrary(java.lang.String), NullPointerException
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public static long nanoTime() - Geek's Notes:
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public static final PrintStream out - See Also:
PrintStream.println(java.lang.String), PrintStream.println(java.lang.Object), PrintStream.println(long), PrintStream.println(int), PrintStream.println(float), PrintStream.println(double), PrintStream.println(char[]), PrintStream.println(char), PrintStream.println(boolean), PrintStream.println()
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public static void runFinalization() - Geek's Notes:
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@Deprecated
public static void runFinalizersOnExit(boolean value) - See Also:
SecurityManager.checkExit(int), Runtime.gc(), Runtime.exit(int), SecurityException
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public static void setErr(PrintStream err) - See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), SecurityException
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[1539]Direct error messages to a file
By Anonymous on 2005/09/22 14:47:49 Rate
// direct messages to a file
Stream st = new Stream ( new FileOutputStream ( "systemerr.txt" ) ) ;
System.setErr ( st ) ;
public static void setIn(InputStream in) - See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), SecurityException
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public static void setOut(PrintStream out) - See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), SecurityException
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[1540]Direct console messages to a file
By Anonymous on 2005/09/22 15:10:03 Rate
// direct messages to a file
Stream st = new Stream ( new FileOutputStream ( "systemout.txt" ) ) ;
System.setOut ( st ) ;
public static void setProperties(Properties props) - See Also:
SecurityManager.checkPropertiesAccess(), SecurityException, getProperties(), getProperty(String)
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- Description Add your codes or notes Search More Java Examples
public static String setProperty(String key,
String value)- See Also:
SecurityManager.checkPermission(java.security.Permission), PropertyPermission, getProperty(java.lang.String, java.lang.String), getProperty(java.lang.String), IllegalArgumentException, NullPointerException, SecurityException
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public static void setSecurityManager(SecurityManager s) - See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), getSecurityManager(), SecurityException
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