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  • Initialize an object in java

    - by harigm
    Is it the right Way we initialise the the object? I have a class Sample I want to initialise the Object in my Sample1 Class After intialisation I dont require to use the object of Sample Class. In that Case Can I initialise that object as new Sample(); instead of Sample s = new Sample(); if I am not going to use s anywhere in my Sample1 Class My question, is this a good practice to do that? will there be any after affects

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  • initiliase the object in java

    - by harigm
    is it the right Way we initialise the the object? I have a Class Sample(); I want to intialise the Object in my Sample1 Class After intialisation I dont require to use the object of Sample Class. In that Case Can I initialise that object as new Sample(); instead of Sample s = new Sample(), if I am not going to use s anywhere in my Sample1 Class My question, is this a good practice to do that? will there be any after affects

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  • How to set java_home on Windows 7?

    - by Derek
    I went to the Environment Variables in 'System' in the control panel and made 2 new variables. one for user variables and one for system variables, both named JAVA_HOME and both pointing to C:\Sun\SDK\jdk\bin but for some reason, I still get the below error when running a java command... BUILD FAILED C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:161: The following error occurred while executing this line: C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:141: The following error occurred while executing this line: C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:137: Please set java.home to a JDK installation Total time: 1 second C:\Users\Derek\Desktop\eclipse\eclipse\glassfish>lib\ant\bin\ant -f setup.xml Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre6\lib\tools.jar Buildfile: setup.xml

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  • java.lang.UnsupportedClassVersionError: Bad version number in .class file?

    - by grmn.bob
    I am getting this error when I include an opensource library that I had to compile from source. Now, all the suggestions on the web indicate that the code was compiled in one version and executed in another version (new on old). However, I only have one version of JRE on my system. If I run the commands: $ javac -version javac 1.5.0_18 $ java -version java version "1.5.0_18" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_18-b02) Java HotSpot(TM) Server VM (build 1.5.0_18-b02, mixed mode) and check in Eclipse for the properties of the java library, I get 1.5.0_18 Therefore, I have to conclude something else, internal to a class itself, is throwing the exception?? Is that even possible?

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  • Is J2EE/EJBs a dying trend?

    - by Taranfx
    I might be wrong on this, but I no longer see heavy Business and Web services being hosted using J2ee technologies (Especially EJBs). Having known the power and scalability of J2ee applications, what is keeping developers/decision makers to restrict themselves to Core Java (POJOs) or even other web technologies like PHP, python. Is it the development time? Is it the Ease of configuration? (I feel this should not be a strong reason with Java EE 6, things are simplified) Of course scripting languages are faster to develop, we cannot ignore the fact that they are inherently not-as-scalable as Java Applications are (using App servers)

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  • java.lang.IllegalStateException: Parent was not null, but this component not related

    - by Muneeswaran Balasubramanian
    Hi to all, I have the following exception at the time of running jsf program. org.apache.jasper.JasperException: An exception occurred processing JSP page /pages/general/internalServerErrorPage.jsp at line 44 41: <link rel="shortcut icon" href="<%=request.getContextPath()%>/resources/images/infomindzicon.ico" type="image/x-icon" /> 42: </head> 43: <body id="sscmsMainBody"> 44: <h:form id="internalServerErrorPageForm" binding="#{ServerErrorBean.initForm}"> 45: <rich:page id="richPage" theme="#{LayoutSkinBean.layoutTheme}" 46: width="#{LayoutSkinBean.layoutScreenWidth}" 47: sidebarWidth="0"> Caused by: javax.servlet.ServletException: javax.servlet.jsp.JspException: java.lang.IllegalStateException: Parent was not null, but this component not related at org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858) at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791) at org.apache.jsp.pages.general.internalServerErrorPage_jsp._jspService(internalServerErrorPage_jsp.java:207) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377) What is the meaning of this exception and how can i resolve this?Please help me.Thanks in advance.

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  • Why is J2ee/EJBs a dying Trend?

    - by Taranfx
    I might be wrong on this, but I no longer see heavy Business and Web services being hosted using J2ee technologies (Especially EJBs). Having known the power and scalability of J2ee applications, what is keeping developers/decision makers to restrict themselves to Core Java (POJOs) or even other web technologies like PHP, python. Is it the development time? Is it the Ease of configuration? (I feel this should not be a strong reason with Java EE 6, things are simplified) Of course scripting languages are faster to develop, we cannot ignore the fact that they are inherently not-as-scalable as Java Applications are (using App servers)

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  • substring IP address in java

    - by m2010
    This program takes string like that 192.168.1.125 and cut every number then converts it to integer, but it returns an error. import java.lang.String; import java.lang.Number; import java.lang.Integer; class Ip { public static void main ( String [] args ) { int i ; i = args[0].indexOf ( '.' ); do { if ( i != -1 ) args[0].substring ( 0, i ); String str = args[0].substring ( i + 1, args[0].length() ); String str2 = Integer.parseInt ( str ); System.out.println ( str2 ); } while ( i != -1 ); } }

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  • Java: how to initialize int without assigning a value?

    - by HH
    $ javac InitInt.java InitInt.java:9: '[' expected right = new int; ^ InitInt.java:9: ']' expected right = new int; ^ InitInt.java:13: ';' expected } ^ InitInt.java:14: ';' expected public int getRight(){return right;} ^ InitInt.java:15: reached end of file while parsing } ^ 5 errors $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? right = new int; // later assiging a value } public int getRight(){return right;} }

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  • how to pass an id number string to this class

    - by Phil
    I'm very much a vb person, but have had to use this id number class in c#. I got it from http://www.codingsanity.com/idnumber.htm : using System; using System.Text.RegularExpressions; namespace Utilities.SouthAfrica { /// <summary> /// Represents a South African Identity Number. /// valid number = 7707215230080 /// invalid test number = 1234567891234 /// /// </summary> [Serializable()] public class IdentityNumber { #region Enumerations /// <summary> /// Indicates a gender. /// </summary> public enum PersonGender { Female = 0, Male = 5 } public enum PersonCitizenship { SouthAfrican = 0, Foreign = 1 } #endregion #region Declarations static Regex _expression; Match _match; const string _IDExpression = @"(?<Year>[0-9][0-9])(?<Month>([0][1-9])|([1][0-2]))(?<Day>([0-2][0-9])|([3][0-1]))(?<Gender>[0-9])(?<Series>[0-9]{3})(?<Citizenship>[0-9])(?<Uniform>[0-9])(?<Control>[0-9])"; #endregion #region Constuctors /// <summary> /// Sets up the shared objects for ID validation. /// </summary> static IdentityNumber() { _expression = new Regex(_IDExpression, RegexOptions.Compiled | RegexOptions.Singleline); } /// <summary> /// Creates the ID number from a string. /// </summary> /// <param name="IDNumber">The string ID number.</param> public IdentityNumber(string IDNumber) { _match = _expression.Match(IDNumber.Trim()); } #endregion #region Properties /// <summary> /// Indicates the date of birth encoded in the ID Number. /// </summary> /// <exception cref="System.ArgumentException">Thrown if the ID Number is not usable.</exception> public DateTime DateOfBirth { get { if(IsUsable == false) { throw new ArgumentException("ID Number is unusable!", "IDNumber"); } int year = int.Parse(_match.Groups["Year"].Value); // NOTE: Do not optimize by moving these to static, otherwise the calculation may be incorrect // over year changes, especially century changes. int currentCentury = int.Parse(DateTime.Now.Year.ToString().Substring(0, 2) + "00"); int lastCentury = currentCentury - 100; int currentYear = int.Parse(DateTime.Now.Year.ToString().Substring(2, 2)); // If the year is after or at the current YY, then add last century to it, otherwise add // this century. // TODO: YY -> YYYY logic needs thinking about if(year > currentYear) { year += lastCentury; } else { year += currentCentury; } return new DateTime(year, int.Parse(_match.Groups["Month"].Value), int.Parse(_match.Groups["Day"].Value)); } } /// <summary> /// Indicates the gender for the ID number. /// </summary> /// <exception cref="System.ArgumentException">Thrown if the ID Number is not usable.</exception> public PersonGender Gender { get { if(IsUsable == false) { throw new ArgumentException("ID Number is unusable!", "IDNumber"); } int gender = int.Parse(_match.Groups["Gender"].Value); if(gender < (int) PersonGender.Male) { return PersonGender.Female; } else { return PersonGender.Male; } } } /// <summary> /// Indicates the citizenship for the ID number. /// </summary> /// <exception cref="System.ArgumentException">Thrown if the ID Number is not usable.</exception> public PersonCitizenship Citizenship { get { if(IsUsable == false) { throw new ArgumentException("ID Number is unusable!", "IDNumber"); } return (PersonCitizenship) Enum.Parse(typeof(PersonCitizenship), _match.Groups["Citizenship"].Value); } } /// <summary> /// Indicates if the IDNumber is usable or not. /// </summary> public bool IsUsable { get { return _match.Success; } } /// <summary> /// Indicates if the IDNumber is valid or not. /// </summary> public bool IsValid { get { if(IsUsable == true) { // Calculate total A by adding the figures in the odd positions i.e. the first, third, fifth, // seventh, ninth and eleventh digits. int a = int.Parse(_match.Value.Substring(0, 1)) + int.Parse(_match.Value.Substring(2, 1)) + int.Parse(_match.Value.Substring(4, 1)) + int.Parse(_match.Value.Substring(6, 1)) + int.Parse(_match.Value.Substring(8, 1)) + int.Parse(_match.Value.Substring(10, 1)); // Calculate total B by taking the even figures of the number as a whole number, and then // multiplying that number by 2, and then add the individual figures together. int b = int.Parse(_match.Value.Substring(1, 1) + _match.Value.Substring(3, 1) + _match.Value.Substring(5, 1) + _match.Value.Substring(7, 1) + _match.Value.Substring(9, 1) + _match.Value.Substring(11, 1)); b *= 2; string bString = b.ToString(); b = 0; for(int index = 0; index < bString.Length; index++) { b += int.Parse(bString.Substring(index, 1)); } // Calculate total C by adding total A to total B. int c = a + b; // The control-figure can now be determined by subtracting the ones in figure C from 10. string cString = c.ToString() ; cString = cString.Substring(cString.Length - 1, 1) ; int control = 0; // Where the total C is a multiple of 10, the control figure will be 0. if(cString != "0") { control = 10 - int.Parse(cString.Substring(cString.Length - 1, 1)); } if(_match.Groups["Control"].Value == control.ToString()) { return true; } } return false; } } #endregion } } Here is the code from my default.aspx.cs page: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using Utilities.Southafrica; <- this is the one i added to public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { var someNumber = new IdentityNumber("123456"); <- gives error } } Can someone please tell the syntax for how I pass an id number to the class? Thanks

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  • Besides EAR and EJB, what do I get from a J2EE app server that I don't get in a servlet container li

    - by dacracot
    We use Tomcat to host our WAR based applications. We are servlet container compliant J2EE applications with the exception of org.apache.catalina.authenticator.SingleSignOn. We are being asked to move to a commercial J2EE application server. The first downside to changing that I see is the cost. No matter what the charges for the application server, Tomcat is free. Second is the complexity. We don't use either EJB nor EAR features (of course not, we can't), and have not missed them. What then are the benefits I'm not seeing? What are the drawbacks that I haven't mentioned? Mentioned were... JTA - Java Transaction API - We control transaction via database stored procedures. JPA - Java Persistence API - We use JDBC and again stored procedures to persist. JMS - Java Message Service - We use XML over HTTP for messaging. This is good, please more!

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  • Grails: Querying Associations causes groovy.lang.MissingMethodException

    - by Paul
    Hi, I've got an issue with Grails where I have a test app with: class Artist { static constraints = { name() } static hasMany = [albums:Album] String name } class Album { static constraints = { name() } static hasMany = [ tracks : Track ] static belongsTo = [artist: Artist] String name } class Track { static constraints = { name() lyrics(nullable: true) } Lyrics lyrics static belongsTo = [album: Album] String name } The following query (and a more advanced, nested association query) works in the Grails Console but fails with a groovy.lang.MissingMethodException when running the app with 'run-app': def albumCriteria = tunehub.Album.createCriteria() def albumResults = albumCriteria.list { like("name", receivedAlbum) artist { like("name", receivedArtist) } // Fails here maxResults(1) } Stacktrace: groovy.lang.MissingMethodException: No signature of method: java.lang.String.call() is applicable for argument types: (tunehub.LyricsService$_getLyrics_closure1_closure2) values: [tunehub.LyricsService$_getLyrics_closure1_closure2@604106] Possible solutions: wait(), any(), wait(long), each(groovy.lang.Closure), any(groovy.lang.Closure), trim() at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy:61) at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy) (...truncated...) Any pointers?

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  • Java newbie problem: classes of the same package accessing one another?

    - by HH
    Test.java and SetWord.java belong to the package tools. Test.java needs to access SetWord but an odd error 'cannot find' SetWord appear. The package limits the visibility, it works without 'package tools;' lines. How can I acess the SetWords with Test in the same pkg? In general, how can classes access one another in the same pkg? Test.java package tools; import java.io.*; import java.util.*; public class Test{ public static void main(String[] args) { //IT CANNOT FIND SetWords despite the same folder, why? SetWord sw=new SetWord(); System.out.println(st.set("HELLO)"); } } SetWord.java package tools; import java.io.*; import java.util.*; public class SetWord{ public SetWord(){} public String set(String s) { return s.trim().toLowerCase(); } }

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  • casting a generic array in java

    - by liloboy
    The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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  • How to fix Eclipse validation error "No grammar constraints detected for the document"?

    - by Casey
    Eclipse 3.5.2 is throwing an XML schema warning message: No grammar constraints (DTD or XML schema) detected for the document. The application.xml file: <?xml version="1.0" encoding="UTF-8"?> <application xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/application_5.xsd" version="5"> </application> I do not want to disable the warning. How can I get Eclipse to correctly validate the XML document?

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  • Accessing the next 3 element values in a Map knowing the key.

    - by Rachel
    I have java.util.LinkedHashMap with Integer as Key and Character as Value. I know the key of the element i want to access. In addition to the element value for the key, i also want to retrieve the next 3 element values so that i can append all the 4 element values and form a string with 4 chars. I am asking for something like how we will do in a java.util.List. Is this feasible by any means in a Map/ordered map? Please suggest any other data structure that can help me achieve this. I am using Java 6.

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  • Why Java cannot find my constructor?

    - by Roman
    Well, maybe it is a stupid question, but I cannot resolve this problem. In my ServiceBrowser class I have this line: ServiceResolver serviceResolver = new ServiceResolver(ifIndex, serviceName, regType, domain); And compiler complains about it. It says: cannot find symbol symbol : constructor ServiceResolver(int,java.lang.String,java.lang.String,java.lang.String) This is strange, because I do have a constructor in the ServiceResolver: public void ServiceResolver(int ifIndex, String serviceName, String regType, String domain) { this.ifIndex = ifIndex; this.serviceName = serviceName; this.regType = regType; this.domain = domain; } ADDED: I removed void from the constructor and it works! Why?

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  • Has "Killer Game Programming in Java" by Andrew Davison been rendered useless? What new tutorial should I follow? [duplicate]

    - by BDillan
    This question already has an answer here: Killer Game Programming [Java 3D] outdated? 5 answers Its pathetic how it was created in 2005 not so long ago when the Java 3D 1.31 API was released. Now after downloading the source code off the books website and implementing it onto my work-space it cant run. (The 3D Shooter Ch. 23) I downloaded Java 3D 1.5 API, installed it- went back to my source code and javax.media ect.., and EVERY imported class within the game simply couldn't be resolved... they are all outdated.. Please do not say how its meant for a positive curvature in your game development skills. No ~ I got the book to understand how to code 3D textures/particle systems/games. Without seeing results how can I learn? If there is still hope for this book please tell me. Otherwise what other books match this one in Game Programming? This one was very well organized, documented and long. I am not looking for a 3D game prog. book on Java. Rather one that has the same reputation as this one but is a bit newer..

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  • How to ...set up new Java environment - largely interfaces...

    - by Chris Kimpton
    Hi, Looks like I need to setup a new Java environment for some interfaces we need to build. Say our system is X and we need to interfaces to systems A, B and C. Then we will be writing interfaces X-A, X-B, X-C. Our system has a bus within it, so the publishing on our side will be to the bus and the interface processes will be taking from the bus and mapping to the destination system. Its for a vendor based system - so most of the core code we can't touch. Currently thinking we will have several processes, one per interface we need to do. The question is how to structure things. Several of the APIs we need to work with are Java based. We could go EJB, but prefer to keep it simple, one process per interface, so that we can restart them individually. Similarly SOA seems overkill, although I am probably mixing my thoughts about implementations of it compared to the concepts behind it... Currently thinking that something Spring based is the way to go. In true, "leverage a new tech if possible"-style, I am thinking maybe we can shoe horn some jruby into this, perhaps to make the APIs more readable, perhaps event-machine-like and to make the interface code more business-friendly, perhaps even storing the mapping code in the DB, as ruby snippets that get mixed in... but thats an aside... So, any comments/thoughts on the Spring approach - anything more up-to-date/relevant these days. EDIT: Looking a JRuby further, I am tempted to write it fully in JRuby... in which case do we need any frameworks at all, perhaps some gems to make things clearer... Thanks in advance, Chris

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  • How to design highly scalable web services in Java?

    - by Kshitiz Sharma
    I am creating some Web Services that would have 2000 concurrent users. The services are offered for free and are hence expected to get a large user base. In the future it may be required to scale up to 50,000 users. There are already a few other questions that address the issue like - Building highly scalable web services However my requirements differ from the question above. For example - My application does not have a user interface, so images, CSS, javascript are not an issue. It is in Java so suggestions like using HipHop to translate PHP to native code are useless. Hence I decided to ask my question separately. This is my project setup - Rest based Web services using Apache CXF Hibernate 3.0 (With relevant optimizations like lazy loading and custom HQL for tune up) Tomcat 6.0 MySql 5.5 My questions are - Are there alternatives to Mysql that offer better performance for what I'm trying to do? What are some general things to abide by in order to scale a Java based web application? I am thinking of putting my Application in two tomcat instances with httpd redirecting the request to appropriate tomcat on basis of load. Is this the right approach? Separate tomcat instances can help but then database becomes the bottleneck since both applications access the same database? I am a programmer not a Db Admin, how difficult would it be to cluster a Mysql database (or, to cluster whatever database offered as an alternative to 1)? How effective are caching solutions like EHCache? Any other general best practices? Some clarifications - Could you partition the data? Yes we could but we're trying to avoid it. We need to run a lot of data mining algorithms and the design would evolve over time so we can't be sure what lines of partition should be there.

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  • Is the output of Eclipse's incremental java compiler used in production? Or is it simply to support Eclipse's features?

    - by Doug T.
    I'm new to Java and Eclipse. One of my most recent discoveries was how Eclipse comes shipped with its own java compiler (ejc) for doing incremental builds. Eclipse seems to by default output incrementally built class files to the projRoot/bin folder. I've noticed too that many projects come with ant files to build the project that uses the java compiler built into the system for doing the production builds. Coming from a Windows/Visual Studio world where Visual Studio is invoking the compiler for both production and debugging, I'm used to the IDE having a more intimate relationship with the command-line compiler. I'm used to the project being the make file. So my mental model is a little off. Is whats produced by Eclipse ever used in production? Or is it typically only used to support Eclipse's features (ie its intellisense/incremental building/etc)? Is it typical that for the final "release" build of a project, that ant, maven, or another tool is used to do the full build from the command line? Mostly I'm looking for the general convention in the Eclipse/Java community. I realize that there may be some outliers out there who DO use ecj in production, but is this generally frowned upon? Or is this normal/accepted practice?

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  • Why does Java allow to implement different interfaces, each containing a method with the same signature?

    - by Software Engeneering Learner
    I've recently found that I can have two interfaces containing method with the same signature as a method in the other interface. And then I can have an interface or class that implements both of that interfaces. So the descendant class/interface has implicitly implements two different methods as a one method. Why is this allowed in Java? I can see a numerous problems that arises from that. Even eclipse only can find out about implementations for only one interface method, but for the second one it doesn't show any implementations at all. Also I believe there would be problems with automatic refactoring, like when you would like to change the signature of the method in one of the interfaces and IDE won't be able to correctly change that signature in all implementations, as they implement two different interfaces and how will IDE know what interface method it implementation descends. Why don't just make a compiler error like 'interfaces method names clashes' or something like that?

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  • Why should most logic be in the monitor objects and not in the thread objects when writing concurrent software in Java?

    - by refuser
    When I took the Realtime and Concurrent programming course our lecturer told us that when writing concurrent programs in Java and using monitors, most of the logic should be in the monitor and as little as possible in the threads that access it. I never really understood why and I really would like to. Let me clarify. In this particular case we had several classes. Lift extends Thread Person extends Thread LiftView Monitor, all methods synchronized. This is nothing we came up with, our task was to implement a lift simulation with persons waiting on different floors, and theses were the class skeletons that were given. Then our lecturer said to implement most of the logic in the monitor (he was talking about class Monitor as THE monitor) and as little as possible in the threads. Why would he make a statement like that?

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  • How to remove java.sql.BatchUpdateException in Grails? [closed]

    - by aman.nepid
    I have a domain like this: class BusinessOrganization { static hasMany = [organizationBusinessTypes:OrganizationBusinessType] String name String icon static constraints = { name(blank:false,unique:true) icon(unique:true) } String toString() { return "${name}" } } When I save some data for first time it works fine. But when by the next time it shows this error : Error 500: Internal Server Error URI /nLocatePortal/businessOrganization/save Class java.sql.BatchUpdateException Message Batch entry 0 insert into business_organization (version, icon, name, id) values ('0', '', 'dddd', '2') was aborted. Call getNextException to see the cause. **Around line 24 of grails-app/controllers/com/nlocate/portal/BusinessOrganizationController.groovy** 21: 22: def save() { 23: def businessOrganizationInstance = new BusinessOrganization(params) 24: if (!businessOrganizationInstance.save(flush: true)) { 25: render(view: "create", model: [businessOrganizationInstance: businessOrganizationInstance]) 26: return 27: } Please someone help me why this is happening. I am new to Grails. I have not modified the controllers but still I get this error.

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