Java Try Catch Finally blocks without Catch

Question

I m reviewing some new code   The program has a try and a finally block only   Since the catch block is excluded  how does the try block work if it encounters an exception or anything throwable   Does it just go directly to the finally block

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The Java Language Specification 1  describes how try-catch-finally is executed   Having no catch is equivalent to not having a catch able to catch the given Throwable           If execution of the try block completes abruptly because of a throw of a value V  then there is a choice            If the run-time type of V is assignable to the parameter of any catch clause of the try statement  then               If the run-time type of V is not assignable to the parameter of any catch clause of the try statement  then the finally block is executed  Then there is a choice            If the finally block completes normally  then the try statement completes abruptly because of a throw of the value V      If the finally block completes abruptly for reason S  then the try statement completes abruptly for reason S  and the throw of value V is discarded and forgotten                   1  Execution of try-catch-finally

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how does the try block work if it   encounters an exception or anything   throwable   The exception is thrown out of the block  just as in any other case where it s not caught   The finally block is executed regardless of how the try block is exited -- regardless whether there are any catches at all  regardless of whether there is a matching catch   The catch blocks and the finally are orthogonal parts of the try block  You can have either or both  With Java 7  you ll be able to have neither

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The finally block is executed after the try block completes  If something is thrown inside the try block when it leaves the finally block is executed

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The finally block is always run after the try block ends  whether try ends normally or abnormally due to an exception  er  throwable   If an exception is thrown by any of the code within the try block  then the current method simply re-throws  or continues to throw  the same exception  after running the finally block    If the finally block throws an exception   error   throwable  and there is already a pending throwable  it gets ugly   Quite frankly  I forget exactly what happens  so much for my certification years ago    I think both throwables get linked together  but there is some special voodoo you have to do  i e  - a method call I would have to look up  to get the original problem before the  finally  barfed  er  threw up   Incidentally  try finally is a pretty common thing to do for resource management  since java has no destructors   E g  -   r   new LeakyThing    try   useResource  r     finally   r release          close  destroy  etc    Finally   one more tip   if you do bother to put in a catch  either catch specific  expected  throwable subclasses  or just catch  Throwable   not  Exception   for a general catch-all error trap   Too many problems  such as reflection goofs  throw  Errors   rather than  Exceptions   and those will slip right by any  catch all  coded as   catch   Exception e          doesn t really catch  all   eh    do this instead   catch   Throwable t

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The inner finally is executed prior to throwing the exception to the outer block    public class TryCatchFinally      public static void main String   args  throws Exception        try          System out println  A            try              System out println  B                throw new Exception  threw exception in B                      finally                       System out println  X                        any code here in the first try block            is unreachable if an exception occurs in the second try block           catch Exception e                System out println  Y              finally               System out println  Z                  Results in  A B X Y Z

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Regardless of exception thrown or not in try block - finally block will be executed  Exception would not be caught

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A small note on try finally  The finally will always execute unless   System exit   is called  The JVM crashes  The try   block never ends  e g  endless loop

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Inside try block we write codes that can throw an exception  The catch block is where we handle the exception  The finally block is always executed no matter whether exception occurs or not   Now if we have try-finally block instead of try-catch-finally block then the exception will not be handled and after the try block instead of control going to catch block it will go to finally block  We can use try-finally block when we want to do nothing with the exception

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Don t you try it with that program  It ll goto finally block and executing the finally block  but  the exception won t be handled  But  that exception can be overruled in the finally block

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If any of the code in the try block can throw a checked exception  it has to appear in the throws clause of the method signature   If an unchecked exception is thrown  it s bubbled out of the method     The finally block is always executed  whether an exception is thrown or not

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Java versions before version 7 allow for these three combinations of try-catch-finally     try - catch try - catch - finally try - finally   finally block will be always executed no matter of what s going on in the try or and catch block  so if there is no catch block  the exception won t be handled here   However  you will still need an exception handler somewhere in your code - unless you want your application to crash completely of course  It depends on the architecture of your application exactly where that handler is         Java try block must be followed by either catch or finally block    For each try block there can be zero or more catch blocks  but only one finally block    The finally block will not be executed if program exits either by calling System exit   or by causing a fatal error that causes the process to abort

[java] Java Try Catch Finally blocks without Catch

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