Why doesn t catching Exception catch RuntimeException

Question

This is very odd to me  RuntimeException inherits from Exception  which inherits from Throwable   catch Exception exc       won t catch RuntimeException      but  catch Throwable exc       will catch RuntimeException      I know RuntimeException is special in that it s unchecked  But to my understanding that applies just to whether exceptions have to be declared  not whether they are caught  And even then  I don t know why this logic would break on catching Throwable   This is pretty relevant to me since I have a situation where RuntimeException can be thrown in a terminal operation  I m not sure the name for this pattern  but something like  my class EmailRoller takes an array of Callbacks  The code looks like this   for Callback cb   callbacks        try           cb call item             catch Exception exc            logger error  Error in callback     exc            So this is a case where something like an OOME needs to fly through  because if one of these callbacks consumes all machine memory  that sure as heck is going to affect the running of the other ones  But a NullPointerException  Or an IndexOutOfBoundsException  Those will affect the callback but won t prevent the others from running   Also  this is a bit of an enterprise design  Different programmers or teams can add callbacks to process the item  but they should be isolated from each other  This means  as the programmer responsible for insulating these callbacks from each other  I shouldn t rely on them to make sure errors don t slip through  Catching Exception should be about the right line  but it isn t because RuntimeException slips through  So my more general question is  what s a good pattern here  Just catch Exception   RuntimeException exc   which I believe is a syntax error because of the inheritance

User · Answer

catch  Exception ex            WILL catch RuntimeException   Whatever you put in catch block will be caught as well as the subclasses of it

User · Answer

Catching Exception will catch a RuntimeException

User · Answer

The premise of the question is flawed  because catching Exception does catch RuntimeException  Demo code   public class Test       public static void main String   args            try               throw new RuntimeException  Bang              catch  Exception e                System out println  I caught      e                       Output   I caught  java lang RuntimeException  Bang   Your loop will have problems if    callbacks is null anything modifies callbacks while the loop is executing  if it were a collection rather than an array    Perhaps that s what you re seeing

User · Answer

class Test extends Thread       public void run              try                Thread sleep 10000              catch InterruptedException e                 System out println  test1                throw new RuntimeException  Thread interrupted     e                               public static void main String args               Test t1 new Test1              t1 start              try                t1 interrupt               catch Exception e               System out println  test2                System out println  Exception handled   e                            Its output doesn t contain test2   so its not handling runtime exception    jon skeet   Jan Zyka

User · Answer

I faced similar scenario  It was happening because classA s initilization was dependent on classB s initialization  When classB s static block faced runtime exception  classB was not initialized  Because of this  classB did not throw any exception and classA s initialization failed too   class A   this class will never be initialized because class B won t intialize   static      try        classB someStaticMethod         catch Exception e         sysout  This comment will never be printed                class B   this class will never be initialized  static      int i   1 0   throw run time exception       public static void someStaticMethod         And yes   catching Exception will catch run time exceptions as well

[java] Why doesn't catching Exception catch RuntimeException?

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