Can we have try/catch in a static block in a class?

hi All
i have a question about put a try/catch block in a static block in a class to catch exceptions that maybe thrown from using System.xxxx(). in my custom class, i have a static block to initialize some variables using System.xxx(). in case of any error/exception, i need to be able to catch it and let the caller know about it. i tried to put a try/catch block in the static block, and tried to rethrow the exception. but it is not allowed, how would i handle situation like this? thanks for your help and advise in advance.

You could just swallow the exception inside try/catch
block, and instead of throwing it out, just set a
static variable to allow checking from outside
whether the initialization succeeded, or check within
the constructor / methods of this class for
successful initialization, and throw the exception
then. You could even save that exception in a static
variable for later.Ouch, ouch, you're hurting my brain. This would allow someone to ignore a (presumably) fatal error. Throw a RuntimeException as indicated. You can wrap a checked exception in an unchecked one if need be.

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Hi, thank you for reading this post!
We all know that an enum represents a set of constants, but sometimes a class has a restricted set of values as
well. My question is can we have an enum of objects.
Example:
We have a class named Coin
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public class Coin implements Measurable
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Maybe you want something like this:
public enum Coin implements Measurable {
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     NICKEL(0.05, "Nickel"),
     PENNY(0.01, "Penny")
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     private String name;
     Coin(double aValue, String aName)
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Exception in static block + re-instantiating

Hello All,
I have got a number of unit tests and one that is running is causing an exception in a static block of a class which is expected. It throws an ExceptionInInitializerError which I catch in the unit test.
But then another test is running using the same class and this time it should pass and create an instance of the same class as before.
But instead I receive a java.lang.NoClassDefFoundError with no class name. Why? Can't I instantiate a class again once the initialisation had failed?
Regards
Jonas

It's part of the VM Specification.
See [2.17.5 Detailed Initialization Procedure|http://java.sun.com/docs/books/jvms/second_edition/html/Concepts.doc.html#24237]
The first time,
10. Otherwise, the initializers must have completed abruptly by throwing some exception E. If the class of E is not Error or one of its subclasses, then create a new instance of the class ExceptionInInitializerError, with E as the argument, and use this object in place of E in the following step. But if a new instance of ExceptionInInitializerError cannot be created because an OutOfMemoryError occurs, then instead use an OutOfMemoryError object in place of E in the following step.After that,
5. If the Class object is in an erroneous state, then initialization is not possible. Release the lock on the Class object and throw a NoClassDefFoundError.

Problems with static member variables WAS: Why is the static initializer instantiating my class?!

Hi,
I have been hunting down a NullPointerException for half a day to come to
the following conclusion.
My constructor calls a method which uses static variables. Since an intance
of my class is created in the static block when the class is loaded, those
statics are probably not fully initialized yet and the constructor called
from the static block has those null pointer problems.
I've considered moving the initialization of the static variables from the
declaration to the static block. But your code is inserted BEFORE any other
code. Therefore not solving my problem.
Two questions:
1) what would be a solution to my problem? How can I make sure my static
variables are initialized before the enhancer generated code in the static
block calls my constructor? Short of decompiling, changing the code and
recompiling.
2) Why is the enhancing code inserted at the beginning of the static block
and not at the end? The enhancements would be more transparent that way if
the static variables are initialized in the static block.
Thanks,
Eric

Hi Eric,
JDO calls the no-args constructor. Your application should regard this constructor as belonging
primarily to JDO. For example, you would not want to initialize persistent fields to nondefault
values since that effort is wasted by JDO's later initilization to persistent values. Typically all
you want to initialize in the no-args constructor are the transactional and unmanaged fields. This
rule means that you need initialization after construction if your application uses the no-args
constructor and wants persistent fields initialized. On the other hand, if your application really
uses constructors with arguments, and you're initializing persistent fields in the no-args
constructor either unintentionally through field initializers or intentionally as a matter of
consistency, you will find treating the no-args constructor differently helpful.
On the other hand, if Kodo puts its static initializer code first as you report, then it is a bug.
Spec Section 20.16: "The generated static initialization code is placed after any user-defined
static initialization code."
David Ezzio
Eric Borremans wrote:
>
Hi,
I have been hunting down a NullPointerException for half a day to come to
the following conclusion.
My constructor calls a method which uses static variables. Since an intance
of my class is created in the static block when the class is loaded, those
statics are probably not fully initialized yet and the constructor called
from the static block has those null pointer problems.
I've considered moving the initialization of the static variables from the
declaration to the static block. But your code is inserted BEFORE any other
code. Therefore not solving my problem.
Two questions:
1) what would be a solution to my problem? How can I make sure my static
variables are initialized before the enhancer generated code in the static
block calls my constructor? Short of decompiling, changing the code and
recompiling.
2) Why is the enhancing code inserted at the beginning of the static block
and not at the end? The enhancements would be more transparent that way if
the static variables are initialized in the static block.
Thanks,
Eric

Use of functions in static block

Hello,
I have this app containing a static {} block. The reason it's there is to 1) provide a splash screen 2) have input dialog to process input string and check if it's valid in order to load app or not.
In pseudocode it's like this:
1 - get input string with showInputDialog()
2 - check for the input string validity (a valid string is with prefix A-, C- or S-)
3 - if string is valid, load the app
4 - if string is not valid, proceed to step 1.
As you may already see, there is going to be a lot of code (with if-else statements) to check for A-, C- and S- prefixed because I am using indexOf() function which takes only one parameter.
I am considering a way to somehow check recursively, but for this I think I'll need a function to call indexOf() with A-, C-, S- and assess validity for each case.
My question is, is there a way in the static block to have a function? Or can somebody please recommend an efficient approach to checking a string validity with different possibilities inside a static block as in my case, to avoid lots of if-else statements?
P.S. My apologies for initially posting this thread in wrong section.
Thank you!
Victor.

DrClap wrote:
What's a function? And why are you particularly concerned about doing those things in a static initializer as opposed to in some other place?Hi,
Sorry, I'm still thinking c++. I meant method. Something like of the form:
static
boolean valid = false;
while string is not valid
stringfrominput = showInputDialog();
//determine if string is valid
valid = checkvalid(stringfrominput)
//if possible to have
boolean checkvalid(stringfrominput)
recursively process stringfrom input based on A-, S-, or C- prefixes
return boolean value
}I have a jar app. It is Windows-based and runs as a TrayIcon application. If I include this process when class is loaded, this means that the app will be loaded with all its features. But I need to make sure that the app's features will be loaded only if certain conditions are met.
I am not sure how else to approach this requirement without using static {} block.
Thank you,
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Static blocks and inheritence

public class SubClass extends SuperClass {
static {
System.out.println("Sub class being called");
SuperClass.setS("TREX");
public class SuperClass {
protected static String s;
static {
System.out.println("Super being called ");
static public setS(String t) { s= t; }
static public String getS() { return s; }
public static void main(String[] args) {
System.out.println(SubClass.getS());
The above prints
"Super being called"
null
Why is "Sub class being called " not printed? It looks like
the subclass static block never gets called.?

hi
may be i did not something catch right concerning static blocks and inheritence
(jdk1.5x)
please have a look at the following example.
1. static block in subclass is only executed if the static vars are not defined final. why is this?
2. why does not any subclass has its "own" hashtable colors?
thanks
hanspeter
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
import java.util.Hashtable;
abstract class ParentStaticBlock {
     static final Hashtable<Integer, String> colors = new Hashtable<Integer, String>();
     static void putColor(int colNumber, String colName) {
          colors.put(colNumber, colName );
     static String getColorNameFor(int colNumber) {
          return colors.get(colNumber);
final class Child1StaticBlock extends ParentStaticBlock {
     public final static int ROT = 0x00000D;
     public final static int GELB = 0x00000E;
     static {
          System.out.println(" hello, here static block of Child1StaticBlock...");
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          putColor(GELB, "GELB");
final class Child2StaticBlock extends ParentStaticBlock {
     public /*final*/ static int GRUEN = 0x00000A;
     public /*final*/ static int BLAU = 0x00000B;
     static {
          System.out.println(" hello, here static block of Child2StaticBlock...");
          putColor(GRUEN, "GR�N");
          putColor(BLAU, "BLAU");
public class TestChildStaticBlock {
      * @param args
     public static void main(String[] args) {
          int colNo;
          String colBez;
          System.out.println("Static elements class Child1StaticBlock ->");
          colNo = Child1StaticBlock.GELB ;
          colBez = Child1StaticBlock.getColorNameFor(colNo);
          System.out.println("color yellow has number >" + colNo + "< and label >" + colBez + "<");
          System.out.println("");
          System.out.println("Static elements class Child2StaticBlock ->");
          colNo = Child2StaticBlock.BLAU ;
          colBez = Child2StaticBlock.getColorNameFor(colNo);
          System.out.println("color blue has number >" + colNo + "< and label >" + colBez + "<");
          System.out.println("");
          System.out.println("contents of hashtable(s) ->");
          System.out.println("ParentStaticBlock.colors:" + ParentStaticBlock.colors);
          System.out.println("Child1StaticBlock.colors:" + Child1StaticBlock.colors);
          System.out.println("Child2StaticBlock.colors:" + Child2StaticBlock.colors);

Can't find class because of try catch block ?!

Hello,
I'm using the JNI to use a java library from my c++ code.
JNI can't find the "Comverse10" class below, but when i put the try catch block in createMessage in comment, FindClass succeeds ?!
Unfortunatly i need the code inside the try block ;-)
I tried a few things, but none of them worked:
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Can someone tell me what is going on ?!
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Pieter.
//Comverse10 class
public class Comverse10 {
MultimediaMessage message;
/** Creates a new instance of Comverse10 */
public Comverse10() {
public void createMessage() {
TextMediaElement text1 = new TextMediaElement("Pieter");
text1.setColor(Color.blue);
SimpleSlide slide1 = new SimpleSlide();
//if i put this try catch block in comment, it works ?!
try{
slide1.add(text1);
catch(com.comverse.mms.mmspade.api.ElementAlreadyExistsException e){}
MessageContent content = new MessageContent();
content.addSlide(slide1);
this.message = new MultimediaMessage();
message.setContent(content);
message.setSubject("Mijn subjectje");
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//creation of JVM
HRESULT Java::CreateJavaVMdll()
     HRESULT HRv = S_OK;
char classpath[1024];
     jint res;
     if(blog)     this->oDebugLog->Printf("CreateJavaVMdll()");
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          if(blog) oDebugLog->Printf("Can't load jvm.dll");
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          FreeLibrary(hVM);     hVM = NULL;
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     if (res < 0) {
if(blog)     oDebugLog->Printf("Can't create JVM with JNI_CreateJavaVM %d\n",res);
return E_FAIL;
     if(blog)     oDebugLog->Printf("JVM created");
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//finding Comverse10 class:
HRESULT CALLAS MMSComposer::InitializeJNI(void)
     HRESULT HRv=E_FAIL;
     DWORD T=0;
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          if(blog)     oDebugLog->Printf("\nInitializeJNI()");
          bJVM = FALSE;
          jni = new Java(oDebugLog);
          if(jni->CreateJavaVMdll()!=S_OK){
               if(blog)     oDebugLog->Printf("CreateJavaVMdll() failed");
               return HRv;
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          if (jcls == 0) {
if(blog)     oDebugLog->Printf("Can't find Comverse10 class");
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               if (jcls2 == 0) {
                    if(blog)     oDebugLog->Printf("Can't find test class");
                    return HRv;
               if(blog)     oDebugLog->Printf("test class found %08x",jcls2);
return HRv;
          if(blog)     oDebugLog->Printf("Comverse10 class found %08x",jcls);
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return HRv;
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          jni->jobj_comv = jni->env->NewGlobalRef(jobj);
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               if(blog)     oDebugLog->Printf("Can't create global reference to Comverse10 object");
return HRv;
          if(blog)     oDebugLog->Printf("global reference to Comverse10 object %08x created",jni->jobj_comv);
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>
I would guess that the real problem is that that the
exception you are catching is not in the class path
that you are defining.Thanks jschell, that was indeed the case.
I don't have the docs, but I would guess that
FindClass() only returns null if an exception is
thrown. And you are not checking for the exception.
Which would tell you the problem.Ok, i'll remember that. But what with exceptions thrown in my java code, the documents say
// jthrowable ExceptionOccurred(JNIEnv *env);
// Determines if an exception is being thrown. The exception stays being thrown until either the native code calls ExceptionClear(), or the Java code handles the exception
so, what if the java code throws an exception and catches it, will i be able to see that in my c++ code with ExceptionOccurred ?
or
should the java method be declared to throw the exception (and not catch it inside the method)
Again, thank you for your help, it's greatly appreciated !

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Can we have try/catch in a static block in a class?

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