Search Results

Search found 33297 results on 1332 pages for 'java java ee'.

Page 660/1332 | < Previous Page | 656 657 658 659 660 661 662 663 664 665 666 667  | Next Page >

  • "Invalid assignment" error from == operator

    - by Tom
    I was trying to write a simple method: boolean validate(MyObject o) { // propertyA && propertyB are not primitive types. return o.getPropertyA() == null && o.getPropertyB() == null; } And got a strange error on the == null part: Syntax error on token ==. Invalid assignment operator. Maybe my Java is rusty after a season in PLSQL. So I tried a simpler example: Integer i = 4; i == null; // compile error: Syntax error on token ==. Invalid assignment operator. Integer i2 = 4; if (i == null); //No problem How can this be? I'm using jdk160_05. To clarify: I'm not trying to assign anything, just do an && operation between two boolean values. I don't want to do this: if (o.propertyA() == null && o.propertyB() == null) { return true; } else { return false; }

    Read the article

  • JSF: How to forward a request to another page in action?

    - by Satya
    I want to forward request to another page from action class I am using below code in my jsf action : public String submitUserResponse(){ ...... ...... parseResponse(uri,request,response); .... return "nextpage"; } public String parseResponse(String uri,request,response){ if(uri != null){ RequestDispatcher dispatcher = request.getRequestDispatcher(uri); dispatcher.forward(request, response); return null; } ................. .................. return "xxxx"; } "submitUserResponse" method is being called when user clicks the submit button from the jsp and this method returns "nextpage" string here request forwards to next page in normal flow. but in my requirement i will call "submitUserResponse () " which will execute and forwrd request to next page.It is going. but it is displaying some exceptions in server That is : java.lang.IllegalStateException: Cannot forward after response has been committed Here my doubts are: 1.why next lines of code is being executed after forwarding my request using dispatched.forward(uri) . Same thing happening in response.sendRedirect("").

    Read the article

  • Best ways to construct Dynamic Search Conditions for Sql

    - by CoolBeans
    I have always wondered what's the best way to achieve this task. In most web based applications you have to provide search options on many different criteria. Based on what criteria is chosen behind the scene you modify your SQL. Generally, this is how I tend to go about it:- Have a base SQL template. In the base template have conditions like this WHERE [#PRE_COND1] AND [#PRE_COND2] .. so on and so forth. So an example SQL might look something like SELECT NAME,AGE FROM PERSONS [,#TABLE2] [,#TABLE3] WHERE [#PRE_COND1] AND [#PRE_COND2] ORDER BY [#ORD_COND1] AND [#ORD_COND2] etc. During run time after figuring out the all the search criteria user has entered, I replace the [#PRE_COND1]s and [#ORD_COND1]s with the appropriate SQLs and then execute the query. I personally do not like this brute force method. However, I never came across a better approach either. How do you accomplish such tasks generally given you are either using native JDBC or Spring JDBC? It is almost like I need a C MACRO like functionality in Java to do this.

    Read the article

  • Can't display image with Imageview on Android

    - by user1029167
    In my \drawable-mdpi folder, I have an image named: test.jpg In my main.xml file, in my LinearLayout section, I have: <ImageView android:id="@+id/test_image" android:src="@drawable/test" android:layout_width="wrap_content" android:layout_height="wrap_content" /> In my src folder, I have only 1 file, HelloAndroidActivity.java with only the following method: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ImageView image = new ImageView(this); image = (ImageView) findViewById(R.id.test_image); setContentView(image); } This seems to be correct, yet whenever I try to run it, I get The application HelloAndroid (process xxxxx) has stopped unexpectedly. Please try again. The strange part is it previously did display the image, but now it won't and I don't know why. Also, when I comment out the ImageDisplay code, and replace it with TextDisplay code. i.e. TextView tv = new TextView(this); tv.setText("Does this work?"); setContentView(tv); It does display the text. Edit: was asked to post logcat. Link to pastebin.

    Read the article

  • JSP displaying source code instead of executing

    - by DJStroky
    I'm new to jsp and have ran into some trouble. Initially, the jsp file and associated java classes were built and tested fine on a test Tomcat server. Now, they've been transitioned to another server of what I believe is the same setup (except it's linux now instead of windows). But when the jsp page is accessed the source code is displayed instead of the jsp actually executing. I've googled for a while but received no success. I had thought that this page might solve the problem since there was no reference to the jsp file I was using or even the following snippets in my web.xml file in the WEB-INF folder: <servlet> <servlet-name>jsp</servlet-name> <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class> <init-param> <param-name>logVerbosityLevel</param-name> <param-value>WARNING</param-value> </init-param> <load-on-startup>3</load-on-startup> </servlet> <servlet-mapping> <servlet-name>jsp</servlet-name> <url-pattern>*.jsp</url-pattern> </servlet-mapping> I tried inserting these lines and restarting Tomcat, but no success. Any ideas?

    Read the article

  • Randomly Position A Div

    - by Connie
    I'm looking for a way to randomly position a div anywhere on a page (ONCE per load). I'm currently programming a PHP-based fantasy pet simulation game. One of the uncommon items on the game is a "Four Leaf Clover." Currently, users gain "Four Leaf Clovers" through random distribution - but I would like to change that (it's not interactive enough!). What I Am Trying To Do: The idea is to make users search for these "Four Leaf Clovers" by randomly placing this image anywhere on the page: (my rendition of a four leaf clover) I'd like to do this using a Java/Ajax script that generates a div, and then places it anywhere on the page. And does not move it once it's been placed, until the page is reloaded. I've tried so many Google searches, and the closest thing that I've found so far is this (click), from this question. But, removing the .fadein, .delay, and .fadeout stopped the script from working entirely. I'm not by any means a pro with Ajax. Is what I'm trying to do even possible?

    Read the article

  • Cannot make a static reference to the non-static type MyRunnable

    - by kaiwii ho
    Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

    Read the article

  • Coldfusion 8 and HTTP PUT - is there a way to PUT an object?

    - by ciaranarcher
    Hi all We are using EHCache with CF 8 to cache stuff on a central server using a RESTful interface over HTTP. I am trying to cache a cfquery object to the cache server. I can get this to work if I call EHCache direct (i.e. store it in a local cache) but if I try to cache on a remote server over HTTP I am running into problems. The code I am using is as follows: <cfhttp url="http://localhost:8080/myCache/myKey" method="put" result="r" timeout="2" throwonerror="true" > <cfhttpparam type="body" value="#ARGUMENTS.item#" /> </cfhttp> CF doesn't like this reference to #ARGUMENTS.item# and it complains Complex object types cannot be converted to simple values. Can anyone give me an example of how to put an object over http using CF? If this is not possible with CF then a Java example would be the next best thing. Many thanks in advance! PS: I do not want to use serialization to text/JSON etc. as this approach has issues with data integrity and most importantly it's not fast enough.

    Read the article

  • Storing strings from a text file/scanner. Array or built-in?

    - by Flowdorio
    This code snippet is to to read a text file, turn the lines into objects through a different public (non changeable) class(externalClass). The external class does nothing but turn strings (lines from the .txt through nextLine) into objects, and is fully functional. The scanner(scanner3) is assigned to the text file. while (scanner3.hasNext()) { externalClass convertedlines = new externalClass(scanner3.nextLine()); I'm not new to programming, but as I'm new to java, I do not know if this requires me to create an array, or if the returned objects are sorted in some other way. i.e is the "importedlines" getting overwritten with each run of the loop(and I need to introduce an array into the loop), or are the objects stored in some way? The question may seem strange, but with the program I am making it would be harder (but definitely not impossible) if I used an array. Any help would be appreciated. As requested, externalClass: public class exernalClass { private String line; externalClass(String inLine){ line = inLine; } public String giveLine() { return line; } }

    Read the article

  • Most efficient way of checking if Date object and Calendar object are in the same month

    - by Indigenuity
    I am working on a project that will run many thousands of comparisons between dates to see if they are in the same month, and I am wondering what the most efficient way of doing it would be. This isn't exactly what my code looks like, but here's the gist: List<Date> dates = getABunchOfDates(); Calendar month = Calendar.getInstance(); for(int i = 0; i < numMonths; i++) { for(Date date : dates) { if(sameMonth(month, date) .. doSomething } month.add(Calendar.MONTH, -1); } Creating a new Calendar object for every date seems like a pretty hefty overhead when this comparison will happen thousands of times, soI kind of want to cheat a bit and use the deprecated method Date.getMonth() and Date.getYear() public static boolean sameMonth(Calendar month, Date date) { return month.get(Calendar.YEAR) == date.getYear() && month.get(Calendar.MONTH) == date.getMonth(); } I'm pretty close to just using this method, since it seems to be the fastest, but is there a faster way? And is this a foolish way, since the Date methods are deprecated? Note: This project will always run with Java 7

    Read the article

  • Very simple code for number search gives me infinite loop

    - by Joshua
    Hello, I am a newbie Computer Science high school student and I have trouble with a small snippet of code. Basically, my code should perform a basic CLI search in an array of integers. However, what happens is I get what appears to be an infinite loop (BlueJ, the compiler I'm using, gets stuck and I have to reset the machine). I have set break points but I still don't quite get the problem...(I don't even understand most of the things that it tells me) Here's the offending code (assume that "ArrayUtil" works, because it does): import java.util.Scanner; public class intSearch { public static void main(String[] args) { search(); } public static void search() { int[] randomArray = ArrayUtil.randomIntArray(20, 100); Scanner searchInput = new Scanner(System.in); int searchInt = searchInput.nextInt(); if (findNumber(randomArray, searchInt) == -1) { System.out.println("Error"); }else System.out.println("Searched Number: " + findNumber(randomArray, searchInt)); } private static int findNumber(int[] searchedArray, int searchTerm) { for (int i = 0; searchedArray[i] == searchTerm && i < searchedArray.length; i++) { return i; } return -1; } } This has been bugging me for some time now...please help me identify the problem!

    Read the article

  • If statement String trouble

    - by Jeremy Stone
    I'm trying to create a program which takes user input of two words and determines whether or not these words are the same. import java.util.Scanner; public class L7E3 { public static void main(String[] args) { Scanner keyboard = new Scanner(System. in ); String word1, word2; System.out.println("Please enter a word: "); word1 = keyboard.nextLine(); System.out.println("Please enter a word: "); word2 = keyboard.nextLine(); if (word1 == word2) { System.out.println("The words are " + word1 + " and " + word2 + ". These words are the same."); } else { System.out.println("The words are " + word1 + " and " + word2 + ". These words are not the same."); } } } I figured that word1==word2 would have worked to determine whether the two strings were equal, I'm using JGrasp and it goes directly to my else option regardless of input. Am I doing something wrong with strings?

    Read the article

  • How to add support for resizing when using an undecorated JFrame?

    - by Jonas
    I would like to customize my titlebar, minimize-, maximize- and the close-button. So I used setUndecorated(true); on my JFrame, but I still want to be able to resize the window. What is the best way to implement that? I have a border on the RootPane, and I could use MouseListeners on the Border or the RootPane. Any recommendations? import java.awt.Color; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.border.LineBorder; public class UndecoratedFrame extends JFrame { private LineBorder border = new LineBorder(Color.BLUE,2); private JMenuBar menuBar = new JMenuBar(); private JMenu menu = new JMenu("File"); private JMenuItem item = new JMenuItem("Nothing"); public UndecoratedFrame() { menu.add(item); menuBar.add(menu); this.setJMenuBar(menuBar); this.setUndecorated(true); this.getRootPane().setBorder(border); this.setSize(400,340); this.setVisible(true); } public static void main(String[] args) { new UndecoratedFrame(); } }

    Read the article

  • Set JTabbedPane width to constant

    - by msp
    I'm implementing an UI in Java Swing. Therefore I use a JTabbedPane. The tabbedPane has no components at startup. When i add a tab to the tabbedpane, the width of the tabbedpane increases, when i remove the tab, the width resizes to the width at the startup. This should not happen. The tabbedpane is placed on a JPanel which has a gridbag layout. Layout code: Container contentPane = mainFrame.getContentPane(); contentPane.setLayout( new GridBagLayout() ); GridBagConstraints c = new GridBagConstraints(); // add the component tree initComponentTree(); c.gridx = 0; c.gridy = 0; c.gridheight = 1; c.gridwidth = 1; c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.LINE_START; c.weightx = 1; c.weighty = 1; contentPane.add( componentTree, c ); // add the tabbed pane initTabbedPane(); c.gridx = 1; c.weightx = 10; contentPane.add( tabbedPane, c ); // add the status panel initStatusPanel(); c.gridx = 0; c.gridy = 1; c.gridwidth = 2; c.fill = GridBagConstraints.HORIZONTAL; c.anchor = GridBagConstraints.LINE_START; c.weightx = 0; c.weighty = 0; contentPane.add( statusPanel, c ); Hope someone can help!

    Read the article

  • Why would one want to use the public constructors on Boolean and similar immutable classes?

    - by Robert J. Walker
    (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

    Read the article

  • select i th smallest element from array

    - by davit-datuashvili
    i have divide and conqurer method to find i th smalles element from array here is code public class rand_select{ public static int Rand_partition( int a[],int p,int q,int i){ //smallest in a[p..q] if ( p==q) return a[p]; int r=partition (a,p,q); int k=r-p+1; if (i==k) return a[r]; if (i<k){ return Rand_partition(a,p,r-1,i); } return Rand_partition(a,r-1,q,i-k); } public static void main(String[]args){ int a[]=new int []{6,10,13,15,8,3,2,12}; System.out.println(Rand_partition(a,0,a.length-1,7)); } public static int partition(int a[],int p,int q){ int m=a[0]; while ( p<q){ while (p<q && a[p++] <m){ p++; } while (q>p && a[q--]>m){ q--; } int t=a[p]; a[p]=a[q]; a[q]=t; } int k=0; for (int i=0;i<a.length;i++){ if ( a[i]==m){ k=i; } } return k; } } but here is problem java.lang.ArrayIndexOutOfBoundsException please help me

    Read the article

  • IntelliJ inspection -- non-thrown exception

    - by skiaddict1
    This is a follow-up question to 1832203. I'm making it a new question as well, because it seems that posting an answer to a question doesn't change its position on the java page and so I'm worried that it won't get seen. Apologies if I've just stepped on some etiquette toes. I'm an IntelliJ newbie -- started using it two days ago and I'm absolutely head-over-heels in love! One of the things I adore is the code inspections. However... In one of my classes I often create exceptions without throwing them. If I can't turn off (or downgrade) the inspection warning for this then I can see I'm going to end up ignoring inspections on at least that file (if not the entire project), which would be a real pity. I've done a search in the inspection settings for "exception", and found nothing that relates exactly, so I turned them all off just to see, and it's still doing it (even after a rebuild...BTW when are inspections redone? at save? at rebuild? ???), so I would really like some help on how to make this one into an info/typo level -- which I can then ignore. Using the free version, if that makes any difference TIA to all those experienced IntelliJ warriors out there!

    Read the article

  • Eclipse Ant Builder problem

    - by styx777
    I made a custom ant script to automatically create a jar file each time I do a build. This is how it looks like: <?xml version="1.0" encoding="UTF-8"?> <project name="TestProj" basedir="." default="jar"> <property name="dist" value="dist" /> <property name="build" value="bin/test/testproj" /> <target name="jar"> <jar destfile="${dist}/TestProj.jar"> <manifest> <attribute name="Main-Class" value="test.testproj.TestProj" /> </manifest> <fileset dir="${build}" /> </jar> </target> </project> I added it by Right clicking my project properties builders clicked new Ant builder then I specified the location of the above xml file. However, when I run it by doing: java -jar TestProj.jar I get a NoClassDefFoundError test/testproj/TestProj I'm using Eclipse in Ubuntu. TestProj is the name of the class and it's in package test.testproj I'm pretty sure there's something wrong with the manifest and probably the location of the xml file as well but I'm not sure how to fix this. Any ideas?

    Read the article

  • Need help implementing this algorithm with map reduce(hadoop)

    - by Julia
    Hi all! i have algorithm that will go through a large data set read some text files and search for specific terms in those lines. I have it implemented in Java, but I didnt want to post code so that it doesnt look i am searching for someone to implement it for me, but it is true i really need a lot of help!!! This was not planned for my project, but data set turned out to be huge, so teacher told me I have to do it like this. I was reading about MapReduce and thaught that i first do the standard implementation and then it will be more/less easier to do it with mapreduce. But didnt happen, since algorithm is quite stupid and nothing special, and map reduce...i cant wrap my mind around it. So here is shortly pseudo code of my algorithm LIST termList (there is method that creates this list from lucene index) FOLDER topFolder INPUT topFolder IF it is folder and not empty list files (there are 30 sub folders inside) FOR EACH sub folder GET file "CheckedFile.txt" analyze(CheckedFile) ENDFOR END IF Method ANALYZE(CheckedFile) read CheckedFile WHILE CheckedFile has next line GET line FOR(loops through termList) GET third word from line IF third word = term from list append whole line to string buffer ENDIF ENDFOR END WHILE OUTPUT string buffer to file Also, as you can see, each time when "analyze" is called, new file has to be created, i understood that map reduce is difficult to write to many outputs??? I understand mapreduce intuition, and my example seems perfectly suited for mapreduce, but when it comes to do this, obviously I do not know enough and i am STUCK! Please please help.

    Read the article

  • How To Include Transitive Dependencies

    - by Brad Rhoads
    I have 2 gradle projects: an Android app and a RoboSpock test. My build.gradle for the Android app has . . . dependencies { compile fileTree(dir: 'libs', include: '*.jar') compile ('com.actionbarsherlock:actionbarsherlock:4.4.0@aar') { exclude module: 'support-v4' } } . . . and builds correctly by itself, e.g assembleRelease works. I'm stuck getting the test to work. I gets lots of errors such as: package com.google.zxing does not exist Those seem to indicate that the .jar files aren't being picked up. Here's my build.gradle for the test project: buildscript { repositories { mavenLocal() mavenCentral() } dependencies { classpath 'com.android.tools.build:gradle:0.9.+' classpath 'org.robospock:robospock-plugin:0.4.0' } } repositories { mavenLocal() mavenCentral() } apply plugin: 'groovy' dependencies { compile "org.codehaus.groovy:groovy-all:1.8.6" compile 'org.robospock:robospock:0.4.4' } dependencies { compile fileTree(dir: ':android:libs', include: '*.jar') compile (project(':estanteApp')) { transitive = true } } sourceSets.test.java.srcDirs = ['../android/src/', '../android/build/source/r/debug'] test { testLogging { lifecycle { exceptionFormat "full" } } } project.ext { robospock = ":estanteApp" // project to test } apply plugin: 'robospock' As that shows, I've tried adding transitive = true and including the .jar files explicitly. But no matter what I try, I end up with the package does not exist error.

    Read the article

  • Printing the "source" class in a log statement with a log4j wrapper

    - by Dur4ndal
    My application has a homebrew logging class that I'm migrating to using log4j under the covers. However, since I'm using the homebrew class to pass the rest of the application's logging statements to log4j, the output statements are logged as coming from the wrapper class instead of the source class. Is there a way to ensure that the "correct" source is being shown besides creating new org.apache.log4j.Logger instances for every log statement? I've also tried using the Logger.log(String callerFQCN, Priority level, Object message, Throwable t) method, but it doesnt seem to be working, for example: public class Logger2 { public static org.apache.log4j.Logger log4JLogger = org.apache.log4j.Logger.getLogger(Logger2.class); public static void warning(Object source, String message) { log(source, message, Level.WARN, null) } private static void log(Object source, String message, Level level, Throwable t) { String className = source.getClass().getName(); System.out.println("Logging class should be " + className); log4JLogger.log(className, loggingLevel, message, t); } } When called by: public void testWarning() { Logger2.warning(new Integer(3), "This should warn"); } Prints: Logging class should be java.lang.Integer 2010-05-25 10:49:57,152 WARN test.Logger2 - This should warn

    Read the article

  • Apache POI rows number

    - by sys_debug
    I am using Apache POI java and want to get the total number of rows which are not empty. I successfully processed a whole row with all its columns. Now I am assuming that I get an excel sheet with multiple rows and not a single row...so how to go about that? I was thinking of getting total number of rows (int n) and then loop until i<=n but not sure. Suggestions are most welcome :) Note: Apache POI version is 3.8. I am not dealing with Xlsx format...only xls. Yes I tried this code but got 20 in return....which is not possible given I have only 5 rows FileInputStream fileInputStream = new FileInputStream("COD.xls"); HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream); HSSFSheet worksheet = workbook.getSheet("COD"); HSSFRow row1 = worksheet.getRow(3); Iterator rows = worksheet.rowIterator(); int noOfRows = 0; while( rows.hasNext() ) { HSSFRow row = (HSSFRow) rows.next(); noOfRows++; } System.out.println("Number of Rows: " + noOfRows);

    Read the article

  • eliminating duplicate Enum code

    - by Don
    Hi, I have a large number of Enums that implement this interface: /** * Interface for an enumeration, each element of which can be uniquely identified by it's code */ public interface CodableEnum { /** * Get the element with a particular code * @param code * @return */ public CodableEnum getByCode(String code); /** * Get the code that identifies an element of the enum * @return */ public String getCode(); } A typical example is: public enum IMType implements CodableEnum { MSN_MESSENGER("msn_messenger"), GOOGLE_TALK("google_talk"), SKYPE("skype"), YAHOO_MESSENGER("yahoo_messenger"); private final String code; IMType (String code) { this.code = code; } public String getCode() { return code; } public IMType getByCode(String code) { for (IMType e : IMType.values()) { if (e.getCode().equalsIgnoreCase(code)) { return e; } } } } As you can imagine these methods are virtually identical in all implementations of CodableEnum. I would like to eliminate this duplication, but frankly don't know how. I tried using a class such as the following: public abstract class DefaultCodableEnum implements CodableEnum { private final String code; DefaultCodableEnum(String code) { this.code = code; } public String getCode() { return this.code; } public abstract CodableEnum getByCode(String code); } But this turns out to be fairly useless because: An enum cannot extend a class Elements of an enum (SKYPE, GOOGLE_TALK, etc.) cannot extend a class I cannot provide a default implementation of getByCode(), because DefaultCodableEnum is not itself an Enum. I tried changing DefaultCodableEnum to extend java.lang.Enum, but this doesn't appear to be allowed. Any suggestions that do not rely on reflection? Thanks, Don

    Read the article

  • How to avoid concurrent execution of a time-consuming task without blocking?

    - by Diego V
    I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

    Read the article

  • How to send XML data through socket InputStream

    - by THeK3nger
    Hi, I'm trying to write a client-server application in Java with an XML-based protocol. But I have a great problem! See this part of client code: InputStream incoming = skt.getInputStream(); //I get Stream from Socket. OutputStream out = skt.getOutputStream(); [...] XMLSerializer serializer = new XMLSerializer(); //This create an XML document. tosend = WUTPClientWriter.createMessage100(projectid, cpuclock, cpunumber); serializer.setOutputByteStream(out); serializer.serialize(tosend); At this point server fall in deadlock. It wait for EOF but I can't send it because if I use out.close(); or skt.shutdownOutput(); I close Socket and I must keep alive this connection. I can't send '\0' becouse I get Parse Error in the server. How can I do? Can I "close" output stream without close socket? RESOLVED I've created new class XMLStreamOutput and XMLStreamInput with advanced Stream gesture.

    Read the article

< Previous Page | 656 657 658 659 660 661 662 663 664 665 666 667  | Next Page >