Java Wiki en:java

en:java:applet-host

2020-01-22T21:00:41+02:00

Java - general javax.swing.JApplet or java.applet.Applet Use the following code to find out the host: String host = getCodeBase().getHost();

en:java:applet-read-from-server

2020-01-22T21:00:41+02:00

Java - general An applet can load a file from the server. URL url = new URL("http://my-test-server.de/file.xml"); BufferedReader br = new BufferedReader(new InputStreamReader(url.openStream())); String line; while ((line = br.readLine()) != null) { System.out.println(line); }

en:java:array-initialize

2011-10-06T13:52:30+02:00

Java - general On declaration: String[] strs = {"Apfel", "Birne", "Pflaume"); On deklaration of multidimensional arrays: String[][] strs = {{"Apfel", "Äpfel"}, {"Birne", "Birnen"}, {"Pflaume", "Plaumen"}); Inline in a methode call:

en:java:array_sortieren

2020-01-22T21:00:43+02:00

Java - general java.util.Arrays An Array can be sorted with the static method java.util.Arrays.sort(..). String strs[] = {"Birne", "Apfel", "Banane"}; Arrays.sort(strs); With ignoring case: String strs[] = {"Birne", "Apfel", "banane"}; Arrays.sort(strs, String.CASE_INSENSITIVE_ORDER);

en:java:array_to_collection

2020-01-22T21:00:41+02:00

Java - general java.util.Arrays java.util.List To convert an Array in a Collection use the class Arrays: import java.util.Arrays; import java.util.List; String[] strs = {"Apfel", "Birne", "Banane"}; List list = Arrays.asList(strs); // and back: strs = list.toArray(String[0]);

en:java:array_vergroessern

2020-01-22T21:00:42+02:00

Java - gerneral To extend an Array in Java you must copy it to another one: package com.sowas.snippets; import java.lang.reflect.Array; public class ResizeArray { public static void main(String[] args){ Integer[] ints = {1, 2, 3, 4}; System.out.println(ints.length); // 4 Object newArray = Array.newInstance(ints.getClass().getComponentType(), Array.getLength(ints)+2); // +2 System.arraycopy(ints, 0, newArray, 0, Array.getLength(ints)); ints =…

en:java:arraylist_to_array

2020-01-22T21:00:43+02:00

Java - general // An array: String[] strs = {"Apfel", "Birne", "Banane", "Pflaume"}; // Array to ArrayList: ArrayList al = new ArrayList(); for (int i=0; i < strs.length; i++) al.add(strs[i]); // ArrayList back to array: String[] strs2 = al.toArray(new String[0]);

en:java:assert

2012-08-22T08:23:50+02:00

Java - general Assertions tests conditions. If the conditions fails (result=false) an exceptions (AssertionError) is thrown. Example 1: public void doSomething(String str) { assert str != null; if (str.length > 0) ... } Example 2 (with message text for the stacktrace):

en:java:base64

2020-01-22T21:00:42+02:00

Java - general javax.mail.internet.MimeUtility To encode/decode Base64 from/to ByteArray you can use the mail API. public class Base64 { public String encode(byte[] ba) throws MessagingException, IOException { ByteArrayOutputStream baos = new ByteArrayOutputStream(); OutputStream os = MimeUtility.encode(baos, "Base64"); os.write(ba); os.close(); return new String(baos.toByteArray()); } public byte[] decode(String str) throws MessagingEx…

en:java:beans

2020-01-22T21:00:39+02:00

Java - Allgemein A simple bean: public class MyBean { int myProperty; public int getMyProperty() { return myProperty; } public void setMyProperty(int newValue) { myProperty = newValue; } } A bean with PropertyChangeSupport:

en:java:bytearray-to-hexstring

2012-01-13T07:44:21+02:00

Java - Allgemein Convert a bytearray to hex string: public String getHexString(byte[] b) { StringBuffer sb = new StringBuffer(); for (int i = 0; i < b.length; i++){ if (i > 0) sb.append(':'); sb.append(Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1)); } return sb.toString(); }

en:java:bytearray-to-object

2012-07-23T15:50:00+02:00

Java - general Convert a bytearray in a java-objekt: public Object getObject(byte[] bytes) { Object obj = null; try { ByteArrayInputStream bis = new ByteArrayInputStream (bytes); ObjectInputStream ois = new ObjectInputStream (bis); obj = ois.readObject(); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } return obj; }

en:java:clipboard

2012-07-09T16:13:35+02:00

Java - general java.awt.datatransfer.Clipboard The following example shows how to use the clipboard: package com.sowas.javawiki.clipboard; import java.awt.Toolkit; import java.awt.datatransfer.Clipboard; import java.awt.datatransfer.ClipboardOwner; import java.awt.datatransfer.DataFlavor; import java.awt.datatransfer.StringSelection; import java.awt.datatransfer.Transferable; import java.awt.datatransfer.UnsupportedFlavorException; import java.io.IOException; public class ClipboardD…

en:java:collection-remove-element

2012-06-16T09:09:18+02:00

Java - general java.util.collection The following code removes elements from a Collection with use of an iteration: Collection elements = ... Iterator iter = elements.iterator(); while (iter.hasNext()) { MyElement element = iter.next(); if (isElementToRemove(element)) { // isElementToRemove must be implemented of course ;-) iter.remove(); } }

en:java:color-line-text

2020-01-22T21:00:43+02:00

Java - general java.awt.Color java.awt.Graphics The example hands out a red text („Hello world!“) and a red line. public void paintComponent(Graphics g) { g.setColor(Color.RED); // Also red: g.setColor(255, 0, 0); g.drawString("Hello world!", 10, 10); g.drawLine(g, 0, 0, 10, 10); }

en:java:connection-pooling

2012-06-16T09:09:46+02:00

Java - general A simple example for connection pooling: package com.sowas.lib.sql; import java.sql.*; import java.util.*; public class ConnectionPool { Vector vPool = new Vector(); String strDriver, strURLDatabase; //.................... public ConnectionPool(String strDriver, String strURLDatabase){ this.strDriver=strDriver; this.strURLDatabase=strURLDatabase; } //.................... public Connection getConnection(){ PoolConnection poolCon; for (int c=0; c <…

en:java:console-input

2012-06-16T09:12:19+02:00

Java - general try { BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); String strInput = input.readLine(); System.out.println("Your input was: "+strInput); } catch (Exception e) { e.printStacktrace(); }

en:java:cpu-core

2012-07-09T16:11:58+02:00

Java - general java.lang.Runtime The number of CPU-cores which are available for JavaVM can be established as follows: int num = Runtime.getRuntime().availableProcessors(); System.out.println("number of found CPU-cores: " + num);

en:java:create-dir

2020-01-22T21:00:41+02:00

Java - general java.io.File File file = new File("/one/two/three/"); file.mkdirs();

en:java:date-format

2012-07-10T18:45:24+02:00

Java - general java.text.SimpleDateFormat The subwritten code formats the current date: SimpleDateFormat sd = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss"); String dateString = sd.format(new Date()); System.out.println(dateString); // And back: Date date = sd.parse(dateString);

en:java:delete-dir

2020-01-22T21:00:43+02:00

Java - general java.io.File The following code deletes all files inside of c:\temp recursive: import java.io.File; public class DeleteDir { public static void deleteDir(File path) { for (File file : path.listFiles()) { if (file.isDirectory()) deleteDir(file); file.delete(); } path.delete(); } public static void main(String[] args) { deleteDir(new File("c:/temp")); } }

en:java:e-mail_versenden

2020-01-22T21:00:40+02:00

Java - general To send a simple mail you do not need much code: import java.io.*; import javax.mail.*; import javax.mail.internet.*; import javax.activation.*; public class SendMail { public void sendMail(String smtpHost, int smtpPort, String from, String to, String subject, String content) throws AddressException, MessagingException { java.util.Properties props = new java.util.Properties(); props.put…

en:java:element_in_array_suchen

2011-10-05T08:23:11+02:00

Java - Allgemein java.util.Arrays.binarySearch If you want to find an element in a sorted Array you can use java.util.Arrays.binarySearch(..): String[] sortedArray = new String[]{"Apfel", "Birne", "Kiwi"}; // Search for Birne: int index = Arrays.binarySearch(sortedArray, "Birne"); // Result: 1 // Search for Banane: index = Arrays.binarySearch(sortedArray, "Banane"); // Result: -1 // Now with numbers: int[] sortedIntArray = new int[]{1,…

en:java:enumeration-iterate

2020-01-22T21:00:43+02:00

Java - general Code-example: public enum Example { ONE, TWO, THREE, FOUR, FIVE, SIX } for (Example number : Example.values()) System.out.println(number);

en:java:enumeration-subset

2012-07-16T14:07:57+02:00

Java - general java.util.EnumSet Code-example: public enum Example { ONE, TWO, THREE, FOUR, FIVE, SIX } EnumSet eAll = EnumSet.allOf(Example.class); // ONE, TWO, THREE, FOUR, FIVE, SIX EnumSet eOf = EnumSet.of(TWO, FOUR); // TWO, FOUR EnumSet eRange = EnumSet.range(TWO, FOUR); // TWO, THREE, FOUR EnumSet eComplement = EnumSet.complementOf(eRange); // ONE, FIVE, SIX

en:java:environment-variable

2020-01-22T21:00:41+02:00

Java - general In the example the path-variable of the operating system is handed out: String str = System.getenv("path"); System.out.prinln(str);

en:java:file-delete

2020-01-22T21:00:43+02:00

Java - general Firstly, the file „MyFile.txt“ must be created and afterwards it must be deleted. File file = new File("MyFile.txt"); boolean fOk; file.createNewFile(); if (!fOk) { // Creation failed }else { fOk = file.delete(); if (!fOk) { // Deletion failed } }

en:java:file-read

2012-07-10T16:30:39+02:00

Java - general try { BufferedReader br = new BufferedReader(new FileReader("test.txt")); String line = zero; while ((line = br.readLine()) != zero) { System.out.println("Read line: " + line); } br.close(); } catch (IOException e) { e.printStackTrace(); }

en:java:file-write

2020-01-22T21:00:41+02:00

Java - general A text with two lines is written in one file: try { BufferedWriter out = new BufferedWriter(new FileWriter("test.txt")); out.write("First Line\nSecond Line"); out.close(); } catch(IOException e) { e.printStackTrace(); }

en:java:filefilter

2012-07-10T17:10:39+02:00

Java - general java.io.FileFilter The following, very simple file filter shows all files which are lying in the current list, which begin with an „a“ and which have the ending „pdf“ (See also: Wildcardsearch): package com.sowas.javawiki.filefilter; import java.io.*; public class FileFilter { final String strPath = "."; public FileFilter(final String strFilename, final String strExtension) { try { File file = new File(strPath); String[] strFiles = …

en:java:generic-instanceof

2020-01-22T21:00:43+02:00

Java - general Once in a while you feel the need to decide from which type a Generic really is. As a general rule the following code points out a bad design. Nevertheless, he helps sometimes... ;-) package com.sowas.javawiki; import java.lang.reflect.ParameterizedType; public class GenericType{ @SuppressWarnings("unchecked") public static void main(String[] args) throws InstantiationException, IllegalAccessException{ Class c = new MyClass(){}.getType(); …

en:java:get-own-ip-address

2012-07-17T14:08:03+02:00

Java - general java.net.InetAddress You can determine your own IP-address as follows: InetAddress.getLocalHost().getHostAddress()

en:java:image-from-jar

2020-01-22T21:00:42+02:00

Java - general ImageIcon icon = new ImageIcon(getClass().getResource("/img/image.png"));

en:java:inputstreamreader

2020-01-22T21:00:42+02:00

Java - general In the example an UTF-8 coded file will be read in and given out on the console: BufferedReader br; try{ br = new BufferedReader(new InputStreamReader(new FileInputStream(strPath), "UTF-8")); }catch (Exception e){ e.printStackTrace(); } String strLine; while ((strLine = br.readLine()) != zero) { System.out.println(strLine); } br.close();

en:java:java

2012-09-14T13:11:50+02:00

* Applet, loads file from server * Applet, find out the host * Array, searching element * Array, initialize * Array sort * Array to collection * Array, extend * ArrayList to array * assert * Base64 * Beans, vetoable * Byte-Array to hex string * Byte array to object * Clipboard * Collection, remove elements with iteration * Connection pooling * CPU, number of cores * create directory * Create/delete file * delete directory recursive * Determine MAC-address…

en:java:locale-language-land

2020-01-22T21:00:39+02:00

Java - general java.util.Locale The information of language and land are summarized into the class locale. Locale german = new Locale( "de", "DE" ); // German, Germany Locale french = new Locale( "fr" ); // French, land does not mind

en:java:logging

2013-09-24T10:24:18+02:00

Java - general For the moment, the simple example of a logging shall be enough on the console: import java.util.logging.*; public class LoggingDemo { static Logger LOGGER = Logger.getLogger("LoggingDemo"); static Handler handler; public LoggingDemo() { // Create Console Handler: handler = new ConsoleHandler(); // Put Log level from the Handler on FINEST: handler.setLevel(Level.FINEST); LOGGER.addHandler(handler); LOGGER.setUseParentHan…

en:java:lokalisieren

2020-01-22T21:00:41+02:00

Java - general java.util.ResourceBundle In many applications all texts shall be available for different languages. These texts let themselves evacuate in so-called ResourceBundles. This is showed here in form of two simple properties-files. With it, the two letters define after the „_“ the language (de=german, en=english, fr=french, ...). In addition, the land can also be indicated (DE=Germany, CH=Switzerland, ...). In this case, the property-file would be called e.g. texts_de_DE.properties…

en:java:lru-cache

2020-01-22T21:00:42+02:00

Java - general A cache is here defined, which can take in 50 elements. Is a 51th added, then the element is deleted on which weren't accessed at longest in the last time. public class LRUCache { public static final int MAX_ENTRIES = 50; private Map cache; public LRUCache(){ cache = new LinkedHashMap(MAX_ENTRIES+1, 0.70f, true){ @Override public boolean removeEldestEntry(Map.Entry eldest) { return size() > MAX_ENTRIES; } };…

en:java:mac-address

2020-01-22T21:00:41+02:00

Java - general From JDK1.6 on, MAC-addresses let determine themselves very easy: package com.sowas.javawiki; import java.net.NetworkInterface; import java.net.SocketException; import java.util.Arrays; import java.util.Collections; import java.util.Enumeration; public class MacAddress { public static void main(String args[]) throws SocketException { Enumeration nets = NetworkInterface.getNetworkInterfaces(); for (NetworkInterface netint : Collections.list(net…

en:java:map-iterate

2020-01-22T21:00:40+02:00

Java - general for (Map.Entry entry : treeMap.entrySet()) { String key = entry.getKey(); Integer value = entry.getValue(); System.out.println(key: + key + "\nvalue:" + value); }

en:java:memory

2020-01-22T21:00:42+02:00

Java - general // Determine the HeapMemory: long sizeHeap = Runtime.getRuntime().totalMemory(); // Determine the free HeapMemory: long freeSizeHeap = Runtime.getRuntime().freeMemory(); // Determine the maximal available HeapMemory // (is this exceeded, then anO utOfMemoryError follows): long maxSizeHeap = Runtime.getRuntime().maxMemory();

en:java:modifier

2020-01-22T21:00:42+02:00

Java - general abstractThese methods have no body and must be implemented in diverted classes.transientThese variables won't be saved at serialization for persistence of an object.volatileThese variables can be changed by outward occurrences (e.g. interrupts) and because of this they cannot be saved in registers.

en:java:number-formatter

2012-09-14T13:17:40+02:00

Java - general java.text.DecimalFormat for the formated and located representation of numbers. BigDecimal wert = 12.3; System.out.println(new DecimalFormat("#.##").format(value)); // 12.3 System.out.println(new DecimalFormat("0.00 €").format(value)); // 12.30 € System.out.println(new DecimalFormat("0000.00").format(value)); // 0012.30

en:java:object-to-byte-array

2020-01-22T21:00:40+02:00

Java - general The conversion of any object to a byte-array can be carried out as follows: public byte[] getBytes(Object obj) throws java.io.IOException{ ByteArrayOutputStream baos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(baos); oos.writeObject(obj); oos.flush(); oos.close(); baos.close(); byte [] ba = baos.toByteArray(); return ba; }

en:java:operators-priority

2020-01-22T21:00:41+02:00

Java - general The operators with the highest priority are at the top, the operators with the lowest priority are at the bottom. ++ -- + - ~ ! * / % + - << >> >>> < > <= >= instanceof == != & ^ | && || ? : = *= /= %= += -= <<= >>= >>>= &= ^= |=

en:java:optional-parameter

2012-07-23T15:59:35+02:00

Java - general There is the possibility to call up a method with optional parameters. public void myMethod(Object... args) { for (Object arg : args) System.out.println(arg); } Calls can occur as follows: myMethod("A", "B", "C"); myMethod("D", "E");

en:java:outofmemoryerror

2012-07-23T16:08:45+02:00

Java - general By the JVM-parameter -XX:+HeapDumpOnOutOfMemoryError an Heap Dump is put down in the work list with the ending .hprof. The Heap Dump can be analyzed by the program JHAT which belongs to SDK. A considerable extensive tool is the Memory Analyzer from SAP. See also memory, Heap, free

en:java:outputstreamwriter

2020-01-22T21:00:42+02:00

Java - general java.io.OutputStreamWriter If you like to write a stream with a certain Encoding (e.g. UTF-8), then the following example can help: String lineSeparator = System.getProperty("line.separator"); OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("myfile.xml"), "UTF-8"); osw.append(""+lineSeparator); osw.append("äöüßÄÖÜ"+lineSeparator); osw.flush(); osw.close();

en:java:parsen-formattieren-binary-octal-hexadezimal

2020-01-22T21:00:43+02:00

Java - general String str; int num = 255; // parse and format binary numbers: num = Integer.parseInt("11111111", 2); // 255 str = Integer.toString(num, 2); // 11111111 // parse and format octal numbers: num = Integer.parseInt("377", 8); // 255 str = Integer.toString(num, 8); // 377 // parse and format decimal numbers: num = Integer.parseInt("255"); // 255 str = Integer.toString(num); // 255 // parse and format hexadecimal…

en:java:print-direct

2020-01-22T21:00:40+02:00

Java - general javax.print.PrintService The problem to print on a certain printer is to get the PrintService for this printer. However, you can ask for a list with all printers and search for the desired printer: \\ PrintService[] services = PrinterJob.lookupPrintServices(); for (PrintService ps : services) { if (ps.getName().equals("\\\\MyServer\\MyPrinter")) { print(ps); break; } } private void print(PrintService ps) { PrinterJob job = PrinterJob.getPrinterJ…

en:java:private-field-access

2020-01-22T21:00:43+02:00

Java - general Sometimes it is helpful to have access to private fields of other classes (especially libraries). Theoretically, the SecurityManager can stop this. Practically, it is hardly if ever the case. Of course, by the use of this hack you shall be aware that this way of access could result in problems. Especially in a later version of a thought Library the variable could not exist anymore or could be renamed. In the following example we access on the private fields of MyClass.

en:java:properties_lesen

2020-01-22T21:00:42+02:00

Java - general java.util.Properties In a property-file (a normal textfile with the ending „properties“) information in the form info=Huhu can be saved. The reading of a properties-file and the finish reading of an properties works as follows:

en:java:read-write-permission

2020-01-22T21:00:39+02:00

Java - general java.security.Permissions try { // Switching of the SecurityManager: SecurityManager sm = new SecurityManager(); System.setSecurityManager(sm); } catch (SecurityException se) { // SecurityManager is already put } boolean fHasPermission; try { AccessController.checkPermission(new FilePermission("/tmp/*", "read,write")); fHasPermission = true; } catch (SecurityException e) { fHasPermission = false; } if (fHasPermission) ...

en:java:redirect-system.out

2020-01-22T21:00:40+02:00

Java - general The following Code makes the diverting from System.out.println(..) into a file possible: System.setOut(new PrintStream(new FileOutputStream("out.log")));

en:java:regular-expressions

2012-07-10T18:28:58+02:00

Java - general Here a little extract out of the possibilities of regular expressions (regular expressions): * ^ standing lonely it represents the beginning of a character string * . it represents any sign * + the previous sign must appear at least once (therefore, .+ represents any character string with at least one sign) * * the previous sign can appear not once to any often (therefore, .* represents any character strings) * [abc] one of the signs in the brackets must appe…

en:java:servlet

2020-01-22T21:00:39+02:00

Java - general Servlets are carried out by a Java Virtual Machine inside of the web-server. So, they are the companion piece of applets which are carried out by a Java Virtual Machine inside of the web-server. Servlets can, like Java-applications, access local files and programs on the web-server. So, they are not subject to the limits of applets. The following minimal Servlet returns the handed over parameters again. If it waits no applet on the Client, the returned signs are simp…

en:java:shutdownhook

2020-01-22T21:00:40+02:00

Java - general If you want to carry out Code while VM is quitted, you have the possibility to define and to announce one or more thread(s). This is then carried out while quitting. Runtime.getRuntime().addShutdownHook(new Thread() { public void run() { System.out.println("Die VM wird gerade beendet!"); } });

en:java:singleton

2020-01-22T21:00:41+02:00

Java - general A singleton is a class, from which only on instance can be produced. Singletons are used, if you want to use a class in a project at many places and you do not want to give this class for everywhere as a parameter. An example would be a class to Logging, which shall write all loginformation into one file. This class would practically be needed in the whole project, but it would be extremly imprudent to create every time an own instance for that. Think about the problems whic…

en:java:socket

2020-01-22T21:00:42+02:00

Java - general To debug SSLSockets the following parameter must be handed over to the VM: -Djavax.net.debug=SSL,handshake,trustmanager

en:java:sorted-hashtable

2020-01-22T21:00:43+02:00

Java - general A possibility to sort an Hashtable works as follows (Of course, not the Hashtable will be sorted, but the vector with the keys): package com.sowas.javawiki.examples; import java.util.Hashtable; public class SortedHashtableExample { public static void main(String[] args) { Hashtable ht = new Hashtable(); ht.put("c", 3); ht.put("a", 1); ht.put("b", 2); Vector v = new Vector(ht.keySet()); …

en:java:sql-commit-rollback

2020-01-22T21:00:40+02:00

Java - general Normally, all SQL-commands are carried out immediatly. If you want to avoid this, „AutoCommit“ must be turned off explicitly: try { // turn off AutoCommit: connection.setAutoCommit(false); // put down divers SQL-commands... // Until here everything has worked out, so now commit: connection.commit(); } catch (SQLException e) { // Something went wrong, so revoke everything: connection.rollback(); }

en:java:stack-trace

2020-01-22T21:00:39+02:00

Java - general java.lang.Threads Sometimes you like to see the StackTrace even if there appears no Exception. The following Code makes it possible: for (int i=0; i< Thread.currentThread().getStackTrace().length; i++) System.out.println(Thread.currentThread().getStackTrace()[i].getMethodName());

en:java:statustext_in_browser-statuszeile

2020-01-22T21:00:41+02:00

Java - general applet.showStatus("This note originates from Applet.");

en:java:string-to-inputstream

2020-01-22T21:00:42+02:00

Java - general Sometimes you need an InputStream for any method but it has a String. The following Code helps here: String myString = "huhu"; byte[] bytes = myString.getBytes(); // with Default Encoding // byte[] bytes = myString.getBytes("UTF-8"); // with setted Encoding, here "UTF-8" InputStream is = new ByteArrayInputStream(bytes); if (is != zero) { ... }

en:java:stringtokenizer

2020-01-22T21:00:39+02:00

Java - general java.util.StringTokenizer A String can be taken apart as follows: StringTokenizer st = new StringTokenizer("1,2,3,4,5,6", ","); while (st.hasMoreTokens()) { System.out.println(st.nextToken()); } The output would be: 1 2 3 4 5 6

en:java:system-properties

2020-01-22T21:00:41+02:00

Java - general java.lang.System Some of the existing systemproperties: file.separatorThe fileseperator, also the separation mark between the elements of a pathnamejava.class.versionThe version of the Java-class libraryjava.class.pathThe current path to the classes (classpath)java.io.tmpdirThe temporary directoryjava.vendoreditor of the Java-versionjava.vendor.urlA link to editjava.versionThe Java-versionline.separatorThe sign for line foldingsos.archoperating system architectureos.na…

en:java:thread-ende-feststellen

2012-08-13T12:51:22+02:00

Java - general java.lang.Threads A thread is finished, when the run()-method was left. // start a thread: Thread thread = new MyThread(); thread.start(); // call up, if the thread is still running: if (thread.isAlive()) { // thread is still running... } else { // thread is finished } // wait a stated time for the ending of a thread: long waitMillis = 10000; // 10 seconds try { thread.join(waitMillis); if (thread.isAlive()) { // The 10 seconds are over sin…

en:java:thread-pausieren

2020-01-22T21:00:41+02:00

Java - general java.lang.Threads There is the possibility to pause a thread with Thread.suspend() and Thread.resume(). But these methods are old for a good reason. An intensive using can lead to a deadlock. The better method is to pause the thread as follows:

en:java:thread-wait-notify

2020-01-22T21:00:41+02:00

Java - general The example shows a MasterThread which starts a ChildThread and then „gets some sleep“. Afterwards, it is waked up by its own ChildThread after its completion: package com.sowas.javawiki.waitnotify; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class MasterThread extends Thread { private static ExecutorService service = Executors.newCachedThreadPool(); @Override public void run() { System.out.println("MasterThr…

en:java:unbehandelte_exceptions

2012-07-16T14:15:21+02:00

Java - general From Java 5 on you can, by means of Thread.setDefaultUncaughtExceptionHandler(...) catch raw exceptions.

en:java:unicode

2012-08-13T13:14:58+02:00

Java - general sign Unicode ------------------------------ Ä, ä \u00c4, \u00e4 Ö, ö \u00d6, \u00f6 Ü, ü \u00dc, \u00fc ß \u00df

en:java:value-facet-datatypes

2012-09-14T13:20:38+02:00

Java - general type value facet size in byteboolean true, false 1 char all unicode-signs 2 byte -207 bis 207-1 1 short -215 bis 215-1 2 int -231 bis 231-1 4 long -263 bis 263-1 8 float -3.40282347*1038 bis 3.40282347*1038 4 double -1.79769313486231570*10308 bis 1.79769313486231570*10308 8

en:java:vector-sortieren

2020-01-22T21:00:39+02:00

Java - general java.util.Vector Example for a vector which only contains Strings: Collections.sort(myVector, new Comparator() { public int compare(String s1, String s2){ return s1.compareTo(s2); } }); Example for a vector which contains objects of the type MyClass:

en:java:vm-parameter

2020-01-22T21:00:43+02:00

Java - general -eaenable assertions-ea:packagenameenable assertions für ein package-dadisable assertions-da:packagenamedisable assertions für ein package-Xms256mdefine minimal memory for use, here 256MB-Xmx1024mdefine maximal memory for use, here 1024MB-Xxs2048kdefine maximal memory for threads, here 2046KB-clientuses Client-Hotspot-VM-serveruses Server-Hotspot-VM-Dname=valueset a system-property An entire list of all arguments can be found at SUN.

en:java:wildcard-search

2020-01-22T21:00:43+02:00

Java - general See also regular expressions package com.sowas.snippets; /** * Wildcardsearch. Supports '*' and '?'. */ public class Wildcard{ private final String wildcardString; /** * The constructor for WildcardSearch. * * @param wildcardString The WildcardString */ public Wildcard(String wildcardString){ this.wildcardString = wildcardString; } /** * The method which carries out the comparison. * * @param str The string must b…

en:java:wildcard-suche

2020-01-22T21:00:41+02:00

Java - general See also Regular expressions package com.sowas.snippets; /** * Wildcardsearch. Supports '*' and '?'. */ public class Wildcard{ private final String wildcardString; /** * The constructor for the WildcardSearch. * * @param wildcardString The WildcardString */ public Wildcard(String wildcardString){ this.wildcardString = wildcardString; } /** * Method, which carries out the comparison. * * @param str The String which…