Does a finally block always get executed in Java

Question

Considering this code  can I be absolutely sure that the finally block always executes  no matter what something   is   try         something          return success        catch  Exception e           return failure        finally         System out println  I don t know if this will get printed out

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This is because you assigned the value of i as 12  but did not return the value of i to the function  The correct code is as follows   public static int test         int i   0      try           return i        finally           i   12          System out println  finally trumps return             return i

User · Answer

Yes  it will  No matter what happens in your try or catch block unless otherwise System exit   called or JVM crashed  if there is any return statement in the block s  finally will be executed prior to that return statement

User · Answer

Answer is simple YES    INPUT   try      int divideByZeroException   5   0    catch  Exception e       System out println  catch        return        also tried with break  in switch-case  got same output   finally       System out println  finally        OUTPUT   catch finally

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Example code   public static void main String   args        System out println Test test        public static int test         try           return 0            finally           System out println  finally trumps return               Output   finally trumps return   0

User · Answer

Yes  it is written here     If the JVM exits while the try or catch code is being executed  then the finally block may not execute  Likewise  if the thread executing the try or catch code is interrupted or killed  the finally block may not execute even though the application as a whole continues

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Here s an elaboration of Kevin s answer  It s important to know that the expression to be returned is evaluated before finally  even if it is returned after   public static void main String   args        System out println Test test        public static int printX         System out println  X        return 0     public static int test         try           return printX              finally           System out println  finally trumps return    sort of              Output   X finally trumps return    sort of 0

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Yes It will  Only case it will not is JVM exits or crashes

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Adding to  vibhash s answer as no other answer explains what happens in the case of a mutable object like the one below   public static void main String   args        System out println test   toString        public static StringBuffer test         StringBuffer s   new StringBuffer        try           s append  sb            return s        finally           s append  updated               Will output   sbupdated

User · Answer

Finally is always run that s the whole point  just because it appears in the code after the return doesn t mean that that s how it s implemented  The Java runtime has the responsibility to run this code when exiting the try block   For example if you have the following   int foo          try           return 42            finally           System out println  done              The runtime will generate something like this   int foo         int ret   42      System out println  done        return 42      If an uncaught exception is thrown the finally block will run and the exception will continue propagating

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Yes  finally will be called after the execution of the try or catch code blocks   The only times finally won t be called are    If you invoke System exit   If you invoke Runtime getRuntime   halt exitStatus  If the JVM crashes first If the JVM reaches an infinite loop  or some other non-interruptable  non-terminating statement  in the try or catch block If the OS forcibly terminates the JVM process  e g   kill -9  lt pid gt  on UNIX If the host system dies  e g   power failure  hardware error  OS panic  et cetera If the finally block is going to be executed by a daemon thread and all other non-daemon threads exit before finally is called

User · Answer

Finally  Block always get executed  Unless and until System exit   statement exists there  first statement in finally block   If system exit   is first statement then finally block won t get executed and control come out of the finally block  Whenever System exit   statement gets in finally block till that statement finally block executed and when System exit   appears then control force fully come out of the finally block

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If an exception is thrown  finally runs  If an exception is not thrown  finally runs  If the exception is caught  finally runs  If the exception is not caught  finally runs   Only time it does not run is when JVM exits

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Here s the official words from the Java Language Specification   14 20 2  Execution of try-finally and try-catch-finally     A try statement with a finally block is executed by first executing the try block  Then there is a choice          If execution of the try block completes normally          If execution of the try block completes abruptly because of a throw of a value V          If execution of the try block completes abruptly for any other reason R  then the finally block is executed  Then there is a choice          If the finally block completes normally  then the try statement completes abruptly for reason R     If the finally block completes abruptly for reason S  then the try statement completes abruptly for reason S  and reason R is discarded           The specification for return actually makes this explicit   JLS 14 17 The return Statement   ReturnStatement       return Expression opt          A return statement with no Expression attempts to transfer control to the invoker of the method or constructor that contains it        A return statement with an Expression attempts to transfer control to the invoker of the method that contains it  the value of the Expression becomes the value of the method invocation       The preceding descriptions say  attempts to transfer control  rather than just  transfers control  because if there are any try statements within the method or constructor whose try blocks contain the return statement  then any finally clauses of those try statements will be executed  in order  innermost to outermost  before control is transferred to the invoker of the method or constructor  Abrupt completion of a finally clause can disrupt the transfer of control initiated by a return statement

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Try this code  you will understand the code in finally block is get executed after return statement   public class TestTryCatchFinally       static int x   0       public static void main String   args           System out println f1              System out println f2                 public static int f1            try              x   1              return x           finally              x   2                       public static int f2            return x

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In addition to the point about return in finally replacing a return in the try block  the same is true of an exception   A finally block that throws an exception will replace a return or exception thrown from within the try block

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Yes  finally block is always execute  Most of developer use this block the closing the database connection  resultset object  statement object and also uses into the java hibernate to rollback the transaction

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Yes It will  Only case it will not is JVM exits or crashes

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Also a return in finally will throw away any exception   http   jamesjava blogspot com 2006 03 dont-return-in-finally-clause html

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If an exception is thrown  finally runs  If an exception is not thrown  finally runs  If the exception is caught  finally runs  If the exception is not caught  finally runs   Only time it does not run is when JVM exits

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I tried the above example with slight modification-  public static void main final String   args        System out println test        public static int test         int i   0      try           i   2          return i        finally           i   12          System out println  finally trumps return               The above code outputs      finally trumps return    2   This is because when return i  is executed i has a value 2  After this the finally block is executed where 12 is assigned to i and then System out out is executed   After executing the finally block the try block returns 2  rather than returning 12  because this return statement is not executed again   If you will debug this code in Eclipse then you ll get a feeling that after executing System out of finally block the return statement of try block is executed again  But this is not the case  It simply returns the value 2

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That s actually true in any language   finally will always execute before a return statement  no matter where that return is in the method body  If that wasn t the case  the finally block wouldn t have much meaning

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Yes  because no control statement can prevent finally from being executed   Here is a reference example  where all code blocks will be executed     x   Current result   Code   --- ---------------- ------ - - -                                                    public static int finallyTest       3                        int x   3                             try                                 try     4                                x      4   return 4                     return x                                   finally     3                                x--    3   throw                        throw new RuntimeException  Ahh                                                                   catch  RuntimeException e      4   return 4                 return   x                               finally     3                            x--                                                                                --- ---------------- ------ - - -       Result  4          In the variant below  return x  will be skipped  Result is still 4   public static int finallyTest         int x   3      try           try               x                if  true  throw new RuntimeException  Ahh                 return x     skipped           finally               x--                  catch  RuntimeException e            return   x        finally           x--            References  of course  track their status  This example returns a reference with value   4   static class IntRef   public int value    public static IntRef finallyTest         IntRef x   new IntRef        x value   3      try           return x        finally           x value       will be tracked even after return

User · Answer

Yes it will get called  That s the whole point of having a finally keyword  If jumping out of the try catch block could just skip the finally block it was the same as putting the System out println outside the try catch

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Consider the following program   public class SomeTest        private static StringBuilder sb   new StringBuilder         public static void main String args               System out println someString             System out println  ---AGAIN---            System out println someString             System out println  ---PRINT THE RESULT---            System out println sb toString                private static String someString              try               sb append  -abc-                return sb toString               finally               sb append  xyz                        As of Java 1 8 162  the above code block gives the following output   -abc- ---AGAIN--- -abc-xyz-abc- ---PRINT THE RESULT--- -abc-xyz-abc-xyz   this means that using finally to free up objects is a good practice like the following code   private static String someString          StringBuilder sb   new StringBuilder         try           sb append  abc            return sb toString           finally           sb   null     Just an example  but you can close streams or DB connections this way

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Yes it will get called  That s the whole point of having a finally keyword  If jumping out of the try catch block could just skip the finally block it was the same as putting the System out println outside the try catch

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Also  although it s bad practice  if there is a return statement within the finally block  it will trump any other return from the regular block  That is  the following block would return false   try   return true    finally   return false      Same thing with throwing exceptions from the finally block

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Consider the following program   public class SomeTest        private static StringBuilder sb   new StringBuilder         public static void main String args               System out println someString             System out println  ---AGAIN---            System out println someString             System out println  ---PRINT THE RESULT---            System out println sb toString                private static String someString              try               sb append  -abc-                return sb toString               finally               sb append  xyz                        As of Java 1 8 162  the above code block gives the following output   -abc- ---AGAIN--- -abc-xyz-abc- ---PRINT THE RESULT--- -abc-xyz-abc-xyz   this means that using finally to free up objects is a good practice like the following code   private static String someString          StringBuilder sb   new StringBuilder         try           sb append  abc            return sb toString           finally           sb   null     Just an example  but you can close streams or DB connections this way

User · Answer

Also a return in finally will throw away any exception   http   jamesjava blogspot com 2006 03 dont-return-in-finally-clause html

User · Answer

Here s the official words from the Java Language Specification   14 20 2  Execution of try-finally and try-catch-finally     A try statement with a finally block is executed by first executing the try block  Then there is a choice          If execution of the try block completes normally          If execution of the try block completes abruptly because of a throw of a value V          If execution of the try block completes abruptly for any other reason R  then the finally block is executed  Then there is a choice          If the finally block completes normally  then the try statement completes abruptly for reason R     If the finally block completes abruptly for reason S  then the try statement completes abruptly for reason S  and reason R is discarded           The specification for return actually makes this explicit   JLS 14 17 The return Statement   ReturnStatement       return Expression opt          A return statement with no Expression attempts to transfer control to the invoker of the method or constructor that contains it        A return statement with an Expression attempts to transfer control to the invoker of the method that contains it  the value of the Expression becomes the value of the method invocation       The preceding descriptions say  attempts to transfer control  rather than just  transfers control  because if there are any try statements within the method or constructor whose try blocks contain the return statement  then any finally clauses of those try statements will be executed  in order  innermost to outermost  before control is transferred to the invoker of the method or constructor  Abrupt completion of a finally clause can disrupt the transfer of control initiated by a return statement

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No  not always one exception case is   System exit 0   before the finally block prevents finally to be  executed     class A       public static void main String args             DataInputStream cin   new DataInputStream System in           try              int i Integer parseInt cin readLine              catch ArithmeticException e            catch Exception e              System exit 0    Program terminates before executing finally block          finally              System out println  Won t be executed                System out println  No error

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The finally block is always executed unless there is abnormal program termination  either resulting from a JVM crash or from a call to System exit 0    On top of that  any value returned from within the finally block will override the value returned prior to execution of the finally block  so be careful of checking all exit points when using try finally

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Consider this in a normal course of execution  i e without any Exception being thrown   if method is not  void  then it always explicitly returns something  yet  finally always gets executed

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Example code   public static void main String   args        System out println Test test        public static int test         try           return 0            finally           System out println  finally trumps return               Output   finally trumps return   0

User · Answer

This is because you assigned the value of i as 12  but did not return the value of i to the function  The correct code is as follows   public static int test         int i   0      try           return i        finally           i   12          System out println  finally trumps return             return i

User · Answer

finally is always executed unless there is abnormal program termination  like calling System exit 0      so  your sysout will get printed

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If you don t handle exception  before terminating the program  JVM executes finally block  It will not executed only if normal execution of program will fail mean s termination of program due to these following reasons     By causing a fatal error that causes the process to abort  Termination of program due to memory corrupt  By calling System exit   If program goes into infinity loop

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Yes it will get called  That s the whole point of having a finally keyword  If jumping out of the try catch block could just skip the finally block it was the same as putting the System out println outside the try catch

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Finally  Block always get executed  Unless and until System exit   statement exists there  first statement in finally block   If system exit   is first statement then finally block won t get executed and control come out of the finally block  Whenever System exit   statement gets in finally block till that statement finally block executed and when System exit   appears then control force fully come out of the finally block

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Yes  finally will be called after the execution of the try or catch code blocks   The only times finally won t be called are    If you invoke System exit   If you invoke Runtime getRuntime   halt exitStatus  If the JVM crashes first If the JVM reaches an infinite loop  or some other non-interruptable  non-terminating statement  in the try or catch block If the OS forcibly terminates the JVM process  e g   kill -9  lt pid gt  on UNIX If the host system dies  e g   power failure  hardware error  OS panic  et cetera If the finally block is going to be executed by a daemon thread and all other non-daemon threads exit before finally is called

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finally is always executed unless there is abnormal program termination  like calling System exit 0      so  your sysout will get printed

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Adding to  vibhash s answer as no other answer explains what happens in the case of a mutable object like the one below   public static void main String   args        System out println test   toString        public static StringBuffer test         StringBuffer s   new StringBuffer        try           s append  sb            return s        finally           s append  updated               Will output   sbupdated

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finally can also be exited prematurely if an Exception is thrown inside a nested finally block  The compiler will warn you that the finally block does not complete normally or give an error that you have unreachable code  The error for unreachable code will be shown only if the throw is not behind a conditional statement or inside a loop   try   finally     try      finally          if someCondition  -- gt  no error because of unreachable code       throw new RunTimeException            int a   5   unreachable code

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Because a finally block will always be called unless you call System exit    or the thread crashes

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try-with-resoruce example  static class IamAutoCloseable implements AutoCloseable       private final String name      IamAutoCloseable String name            this name   name            public void close             System out println name             Test public void withResourceFinally         try  IamAutoCloseable closeable1   new IamAutoCloseable  closeable1             IamAutoCloseable closeable2   new IamAutoCloseable  closeable2              System out println  try          finally           System out println  finally              Test output   try closeable2 closeable1 finally

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I tried this  It is single threaded   public static void main String args    throws Exception       Object obj   new Object        try           synchronized  obj                obj wait                System out println  after wait                      catch  Exception ignored          finally           System out println  finally              The main Thread will be on wait state forever  hence finally will never be called   so console output will not print String  after wait   or finally  Agreed with  Stephen C  the above example is one of the 3rd case mention here   Adding some more such infinite loop possibilities in following code      import java util concurrent Semaphore   public static void main String   args        try              Thread sleep Long MAX VALUE              Thread currentThread   join               new Semaphore 0  acquire               while  true            System out println  after sleep join semaphore exit infinite while loop          catch  Exception ignored          finally           System out println  finally              Case 2  If the JVM crashes first  import sun misc Unsafe  import java lang reflect Field   public static void main String args          try           unsafeMethod              Runtime getRuntime   halt 123           System out println  After Jvm Crash           catch  Exception e          finally           System out println  finally             private static void unsafeMethod   throws NoSuchFieldException  IllegalAccessException       Field f   Unsafe class getDeclaredField  theUnsafe        f setAccessible true       Unsafe unsafe    Unsafe  f get null       unsafe putAddress 0  0       Ref  How do you crash a JVM   Case 6  If finally block is going to be executed by daemon Thread and all other non-daemon Threads exit before finally is called   public static void main String args          Runnable runnable   new Runnable              Override         public void run                 try                   printThreads  Daemon Thread printing                       just to ensure this thread will live longer than main thread                 Thread sleep 10000                 catch  Exception e                  finally                   System out println  finally                                       Thread daemonThread   new Thread runnable       daemonThread setDaemon Boolean TRUE       daemonThread setName  My Daemon Thread        daemonThread start        printThreads  main Thread Printing       private static synchronized void printThreads String str        System out println str       int threadCount   0      Set lt Thread gt  threadSet   Thread getAllStackTraces   keySet        for  Thread t   threadSet            if  t getThreadGroup      Thread currentThread   getThreadGroup                  System out println  Thread      t          state     t getState                   threadCount                      System out println  Thread count started by Main thread     threadCount       System out println  -------------------------------------------------        output  This does not print  finally  which implies  Finally block  in  daemon thread  did not execute     main Thread Printing   Thread  Thread My Daemon Thread 5 main  state BLOCKED   Thread  Thread main 5 main  state RUNNABLE   Thread  Thread Monitor Ctrl-Break 5 main  state RUNNABLE    Thread count started by Main thread 3   -------------------------------------------------   Daemon Thread printing   Thread  Thread My Daemon Thread 5 main  state RUNNABLE   Thread  Thread Monitor Ctrl-Break 5 main  state RUNNABLE   Thread count started by Main thread 2   -------------------------------------------------    Process finished with exit code 0

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That s actually true in any language   finally will always execute before a return statement  no matter where that return is in the method body  If that wasn t the case  the finally block wouldn t have much meaning

User · Answer

Because a finally block will always be called unless you call System exit    or the thread crashes

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The finally block is always executed unless there is abnormal program termination  either resulting from a JVM crash or from a call to System exit 0    On top of that  any value returned from within the finally block will override the value returned prior to execution of the finally block  so be careful of checking all exit points when using try finally

User · Answer

Finally block always execute whether exception  handle or not  if any exception occurred before try block then finally block will not execute

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A logical way to think about this is    Code placed in a finally block must be executed whatever occurs within the try block So if code in the try block tries to return a value or throw an exception the item is placed  on the shelf  till the finally block can execute Because code in the finally block has  by definition  a high priority it can return or throw whatever it likes  In which case anything left  on the shelf  is discarded  The only exception to this is if the VM shuts down completely during the try block e g  by  System exit

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finally is always executed unless there is abnormal program termination  like calling System exit 0      so  your sysout will get printed

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finally is always executed and before returning x s  calculated  value   System out println foo            int foo        int x   2      try          return x          finally          System out println x             Output   3 2

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finally block is executed always even if you put a return statement in the try block  The finally block will be executed before the return statement

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That s actually true in any language   finally will always execute before a return statement  no matter where that return is in the method body  If that wasn t the case  the finally block wouldn t have much meaning

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In addition to the other responses  it is important to point out that  finally  has the right to override any exception returned value by the try  catch block  For example  the following code returns 12   public static int getMonthsInYear         try           return 10            finally           return 12            Similarly  the following method does not throw an exception   public static int getMonthsInYear         try           throw new RuntimeException              finally           return 12            While the following method does throw it   public static int getMonthsInYear         try           return 12                      finally           throw new RuntimeException

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Finally is always called at the end  when you try  it executes some code  if something happens in try  then catch will catch that exception and you could print some mssg out or throw an error  then finally block is executed   Finally is normally used when doing cleanups  for instance  if you use a scanner in java  you should probably close the scanner as it leads to other problems such as not being able to open some file

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I was very confused with all the answers provided on different forums and decided to finally code and see  The ouput is   finally will be executed even if there is return in try and catch block  try       System out println  quot try quot       return      int  i  5 0      System exit 0       catch  Exception e         System out println  quot catch quot      return      int  i  5 0      System exit 0       finally        System out println  quot Print me FINALLY quot       Output  try Print me FINALLY   If return is replaced by System exit 0  in try and catch block in above code and an exception occurs before it for any reason

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A logical way to think about this is    Code placed in a finally block must be executed whatever occurs within the try block So if code in the try block tries to return a value or throw an exception the item is placed  on the shelf  till the finally block can execute Because code in the finally block has  by definition  a high priority it can return or throw whatever it likes  In which case anything left  on the shelf  is discarded  The only exception to this is if the VM shuts down completely during the try block e g  by  System exit

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Yes  it will  No matter what happens in your try or catch block unless otherwise System exit   called or JVM crashed  if there is any return statement in the block s  finally will be executed prior to that return statement

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Yes  it is written here     If the JVM exits while the try or catch code is being executed  then the finally block may not execute  Likewise  if the thread executing the try or catch code is interrupted or killed  the finally block may not execute even though the application as a whole continues

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Yes it will get called  That s the whole point of having a finally keyword  If jumping out of the try catch block could just skip the finally block it was the same as putting the System out println outside the try catch

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Here are some conditions which can bypass a finally block    If the JVM exits while the try or catch code is being executed  then the finally block may not execute  More on sun tutorial   Normal Shutdown - this occurs either when the last non-daemon thread exits OR when Runtime exit    some good blog   When a thread exits  the JVM performs an inventory of running threads  and if the only threads that are left are daemon threads  it initiates an orderly shutdown  When the JVM halts  any remaining daemon threads are abandoned finally blocks are not executed  stacks are not unwound the JVM just exits  Daemon threads should be used sparingly few processing activities can be safely abandoned at any time with no cleanup  In particular  it is dangerous to use daemon threads for tasks that might perform any sort of I O  Daemon threads are best saved for  housekeeping  tasks  such as a background thread that periodically removes expired entries from an in-memory cache  source    Last non-daemon thread exits example     public class TestDaemon       private static Runnable runnable   new Runnable              Override         public void run                 try                   while  true                        System out println  Is alive                        Thread sleep 10                          throw new RuntimeException                                    catch  Throwable t                    t printStackTrace                  finally                   System out println  This will never be executed                                         public static void main String   args  throws InterruptedException           Thread daemon   new Thread runnable           daemon setDaemon true           daemon start            Thread sleep 100              daemon stop            System out println  Last non-daemon thread exits               Output     Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Last non-daemon thread exits  Is alive Is alive Is alive Is alive Is alive

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finally will execute and that is for sure   finally will not execute in below cases    case 1    When you are executing System exit     case 2    When your JVM   Thread crashes   case 3     When your execution is stopped in between manually

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Finally is always run that s the whole point  just because it appears in the code after the return doesn t mean that that s how it s implemented  The Java runtime has the responsibility to run this code when exiting the try block   For example if you have the following   int foo          try           return 42            finally           System out println  done              The runtime will generate something like this   int foo         int ret   42      System out println  done        return 42      If an uncaught exception is thrown the finally block will run and the exception will continue propagating

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I was very confused with all the answers provided on different forums and decided to finally code and see  The ouput is   finally will be executed even if there is return in try and catch block  try       System out println  quot try quot       return      int  i  5 0      System exit 0       catch  Exception e         System out println  quot catch quot      return      int  i  5 0      System exit 0       finally        System out println  quot Print me FINALLY quot       Output  try Print me FINALLY   If return is replaced by System exit 0  in try and catch block in above code and an exception occurs before it for any reason

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That is the whole idea of a finally block  It lets you make sure you do cleanups that might otherwise be skipped because you return  among other things  of course   Finally gets called regardless of what happens in the try block  unless you call System exit int  or the Java Virtual Machine kicks out for some other reason

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Answer is simple YES    INPUT   try      int divideByZeroException   5   0    catch  Exception e       System out println  catch        return        also tried with break  in switch-case  got same output   finally       System out println  finally        OUTPUT   catch finally

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Because the final is always be called in whatever cases you have  You don t have exception  it is still called  catch exception  it is still called

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Yes it will always called but in one situation it not call when you use System exit    try    risky code  catch Exception e     exception handling code   finally      It always execute but before this block if there is any statement like System exit 0   then this block not execute

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No  not always one exception case is   System exit 0   before the finally block prevents finally to be  executed     class A       public static void main String args             DataInputStream cin   new DataInputStream System in           try              int i Integer parseInt cin readLine              catch ArithmeticException e            catch Exception e              System exit 0    Program terminates before executing finally block          finally              System out println  Won t be executed                System out println  No error

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If you don t handle exception  before terminating the program  JVM executes finally block  It will not executed only if normal execution of program will fail mean s termination of program due to these following reasons     By causing a fatal error that causes the process to abort  Termination of program due to memory corrupt  By calling System exit   If program goes into infinity loop

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I tried this  It is single threaded   public static void main String args    throws Exception       Object obj   new Object        try           synchronized  obj                obj wait                System out println  after wait                      catch  Exception ignored          finally           System out println  finally              The main Thread will be on wait state forever  hence finally will never be called   so console output will not print String  after wait   or finally  Agreed with  Stephen C  the above example is one of the 3rd case mention here   Adding some more such infinite loop possibilities in following code      import java util concurrent Semaphore   public static void main String   args        try              Thread sleep Long MAX VALUE              Thread currentThread   join               new Semaphore 0  acquire               while  true            System out println  after sleep join semaphore exit infinite while loop          catch  Exception ignored          finally           System out println  finally              Case 2  If the JVM crashes first  import sun misc Unsafe  import java lang reflect Field   public static void main String args          try           unsafeMethod              Runtime getRuntime   halt 123           System out println  After Jvm Crash           catch  Exception e          finally           System out println  finally             private static void unsafeMethod   throws NoSuchFieldException  IllegalAccessException       Field f   Unsafe class getDeclaredField  theUnsafe        f setAccessible true       Unsafe unsafe    Unsafe  f get null       unsafe putAddress 0  0       Ref  How do you crash a JVM   Case 6  If finally block is going to be executed by daemon Thread and all other non-daemon Threads exit before finally is called   public static void main String args          Runnable runnable   new Runnable              Override         public void run                 try                   printThreads  Daemon Thread printing                       just to ensure this thread will live longer than main thread                 Thread sleep 10000                 catch  Exception e                  finally                   System out println  finally                                       Thread daemonThread   new Thread runnable       daemonThread setDaemon Boolean TRUE       daemonThread setName  My Daemon Thread        daemonThread start        printThreads  main Thread Printing       private static synchronized void printThreads String str        System out println str       int threadCount   0      Set lt Thread gt  threadSet   Thread getAllStackTraces   keySet        for  Thread t   threadSet            if  t getThreadGroup      Thread currentThread   getThreadGroup                  System out println  Thread      t          state     t getState                   threadCount                      System out println  Thread count started by Main thread     threadCount       System out println  -------------------------------------------------        output  This does not print  finally  which implies  Finally block  in  daemon thread  did not execute     main Thread Printing   Thread  Thread My Daemon Thread 5 main  state BLOCKED   Thread  Thread main 5 main  state RUNNABLE   Thread  Thread Monitor Ctrl-Break 5 main  state RUNNABLE    Thread count started by Main thread 3   -------------------------------------------------   Daemon Thread printing   Thread  Thread My Daemon Thread 5 main  state RUNNABLE   Thread  Thread Monitor Ctrl-Break 5 main  state RUNNABLE   Thread count started by Main thread 2   -------------------------------------------------    Process finished with exit code 0

User · Answer

Yes it will always called but in one situation it not call when you use System exit    try    risky code  catch Exception e     exception handling code   finally      It always execute but before this block if there is any statement like System exit 0   then this block not execute

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The finally block will not be called after return in a couple of unique scenarios  if System exit   is called first  or if the JVM crashes   Let me try to answer your question in the easiest possible way   Rule 1   The finally block always run   Though there are exceptions to it  But let s stick to this for sometime    Rule 2   the statements in the finally block run when control leaves a try or a catch block The transfer of control can occur as a result of normal execution  of execution of a break   continue  goto or a return statement  or of a propogation of an exception   In case of a return statement specifically  since its captioned   the control has to leave the calling method   And hence calls the finally block of the corresponding  try-finally structure  The return statement is executed after the finally block   In case there s a return statement in the finally block also  it will definitely override the one pending at the try block   since its clearing the call stack   You can refer a better explanation here   http   msdn microsoft com en-us      the concept is mostly same in all the high level languages

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Same with the following code   static int f         while  true            try               return 1            finally               break                      return 2      f will return 2

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finally can also be exited prematurely if an Exception is thrown inside a nested finally block  The compiler will warn you that the finally block does not complete normally or give an error that you have unreachable code  The error for unreachable code will be shown only if the throw is not behind a conditional statement or inside a loop   try   finally     try      finally          if someCondition  -- gt  no error because of unreachable code       throw new RunTimeException            int a   5   unreachable code

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Here s an elaboration of Kevin s answer  It s important to know that the expression to be returned is evaluated before finally  even if it is returned after   public static void main String   args        System out println Test test        public static int printX         System out println  X        return 0     public static int test         try           return printX              finally           System out println  finally trumps return    sort of              Output   X finally trumps return    sort of 0

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That s actually true in any language   finally will always execute before a return statement  no matter where that return is in the method body  If that wasn t the case  the finally block wouldn t have much meaning

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That is the whole idea of a finally block  It lets you make sure you do cleanups that might otherwise be skipped because you return  among other things  of course   Finally gets called regardless of what happens in the try block  unless you call System exit int  or the Java Virtual Machine kicks out for some other reason

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Finally is always called at the end  when you try  it executes some code  if something happens in try  then catch will catch that exception and you could print some mssg out or throw an error  then finally block is executed   Finally is normally used when doing cleanups  for instance  if you use a scanner in java  you should probably close the scanner as it leads to other problems such as not being able to open some file

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try- catch- finally are the key words for using exception handling case   As normal explanotory  try          code statements        exception thrown here        lines not reached if exception thrown   catch  Exception e          lines reached only when exception is thrown   finally          always executed when the try block is exited       independent of an exception thrown or not     The finally block  prevent executing      When you called System exit 0   If JVM exits  Errors in the JVM

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The finally block is always executed unless there is abnormal program termination  either resulting from a JVM crash or from a call to System exit 0    On top of that  any value returned from within the finally block will override the value returned prior to execution of the finally block  so be careful of checking all exit points when using try finally

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A logical way to think about this is    Code placed in a finally block must be executed whatever occurs within the try block So if code in the try block tries to return a value or throw an exception the item is placed  on the shelf  till the finally block can execute Because code in the finally block has  by definition  a high priority it can return or throw whatever it likes  In which case anything left  on the shelf  is discarded  The only exception to this is if the VM shuts down completely during the try block e g  by  System exit

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Example code   public static void main String   args        System out println Test test        public static int test         try           return 0            finally           System out println  finally trumps return               Output   finally trumps return   0

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A logical way to think about this is    Code placed in a finally block must be executed whatever occurs within the try block So if code in the try block tries to return a value or throw an exception the item is placed  on the shelf  till the finally block can execute Because code in the finally block has  by definition  a high priority it can return or throw whatever it likes  In which case anything left  on the shelf  is discarded  The only exception to this is if the VM shuts down completely during the try block e g  by  System exit

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Consider this in a normal course of execution  i e without any Exception being thrown   if method is not  void  then it always explicitly returns something  yet  finally always gets executed

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try- catch- finally are the key words for using exception handling case   As normal explanotory  try          code statements        exception thrown here        lines not reached if exception thrown   catch  Exception e          lines reached only when exception is thrown   finally          always executed when the try block is exited       independent of an exception thrown or not     The finally block  prevent executing      When you called System exit 0   If JVM exits  Errors in the JVM

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Yes  finally will be called after the execution of the try or catch code blocks   The only times finally won t be called are    If you invoke System exit   If you invoke Runtime getRuntime   halt exitStatus  If the JVM crashes first If the JVM reaches an infinite loop  or some other non-interruptable  non-terminating statement  in the try or catch block If the OS forcibly terminates the JVM process  e g   kill -9  lt pid gt  on UNIX If the host system dies  e g   power failure  hardware error  OS panic  et cetera If the finally block is going to be executed by a daemon thread and all other non-daemon threads exit before finally is called

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Try this code  you will understand the code in finally block is get executed after return statement   public class TestTryCatchFinally       static int x   0       public static void main String   args           System out println f1              System out println f2                 public static int f1            try              x   1              return x           finally              x   2                       public static int f2            return x

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I tried the above example with slight modification-  public static void main final String   args        System out println test        public static int test         int i   0      try           i   2          return i        finally           i   12          System out println  finally trumps return               The above code outputs      finally trumps return    2   This is because when return i  is executed i has a value 2  After this the finally block is executed where 12 is assigned to i and then System out out is executed   After executing the finally block the try block returns 2  rather than returning 12  because this return statement is not executed again   If you will debug this code in Eclipse then you ll get a feeling that after executing System out of finally block the return statement of try block is executed again  But this is not the case  It simply returns the value 2

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Also  although it s bad practice  if there is a return statement within the finally block  it will trump any other return from the regular block  That is  the following block would return false   try   return true    finally   return false      Same thing with throwing exceptions from the finally block

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I tried the above example with slight modification-  public static void main final String   args        System out println test        public static int test         int i   0      try           i   2          return i        finally           i   12          System out println  finally trumps return               The above code outputs      finally trumps return    2   This is because when return i  is executed i has a value 2  After this the finally block is executed where 12 is assigned to i and then System out out is executed   After executing the finally block the try block returns 2  rather than returning 12  because this return statement is not executed again   If you will debug this code in Eclipse then you ll get a feeling that after executing System out of finally block the return statement of try block is executed again  But this is not the case  It simply returns the value 2

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Yes  finally block is always execute  Most of developer use this block the closing the database connection  resultset object  statement object and also uses into the java hibernate to rollback the transaction

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finally is always executed unless there is abnormal program termination  like calling System exit 0      so  your sysout will get printed

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Also  although it s bad practice  if there is a return statement within the finally block  it will trump any other return from the regular block  That is  the following block would return false   try   return true    finally   return false      Same thing with throwing exceptions from the finally block

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In addition to the other responses  it is important to point out that  finally  has the right to override any exception returned value by the try  catch block  For example  the following code returns 12   public static int getMonthsInYear         try           return 10            finally           return 12            Similarly  the following method does not throw an exception   public static int getMonthsInYear         try           throw new RuntimeException              finally           return 12            While the following method does throw it   public static int getMonthsInYear         try           return 12                      finally           throw new RuntimeException

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The finally block will not be called after return in a couple of unique scenarios  if System exit   is called first  or if the JVM crashes   Let me try to answer your question in the easiest possible way   Rule 1   The finally block always run   Though there are exceptions to it  But let s stick to this for sometime    Rule 2   the statements in the finally block run when control leaves a try or a catch block The transfer of control can occur as a result of normal execution  of execution of a break   continue  goto or a return statement  or of a propogation of an exception   In case of a return statement specifically  since its captioned   the control has to leave the calling method   And hence calls the finally block of the corresponding  try-finally structure  The return statement is executed after the finally block   In case there s a return statement in the finally block also  it will definitely override the one pending at the try block   since its clearing the call stack   You can refer a better explanation here   http   msdn microsoft com en-us      the concept is mostly same in all the high level languages

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In addition to the point about return in finally replacing a return in the try block  the same is true of an exception   A finally block that throws an exception will replace a return or exception thrown from within the try block

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Concisely  in the official Java Documentation  Click here   it is written that -      If the JVM exits while the try or catch code is being executed  then   the finally block may not execute  Likewise  if the thread executing   the try or catch code is interrupted or killed  the finally block may   not execute even though the application as a whole continues

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Also  although it s bad practice  if there is a return statement within the finally block  it will trump any other return from the regular block  That is  the following block would return false   try   return true    finally   return false      Same thing with throwing exceptions from the finally block

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finally is always executed and before returning x s  calculated  value   System out println foo            int foo        int x   2      try          return x          finally          System out println x             Output   3 2

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I tried the above example with slight modification-  public static void main final String   args        System out println test        public static int test         int i   0      try           i   2          return i        finally           i   12          System out println  finally trumps return               The above code outputs      finally trumps return    2   This is because when return i  is executed i has a value 2  After this the finally block is executed where 12 is assigned to i and then System out out is executed   After executing the finally block the try block returns 2  rather than returning 12  because this return statement is not executed again   If you will debug this code in Eclipse then you ll get a feeling that after executing System out of finally block the return statement of try block is executed again  But this is not the case  It simply returns the value 2

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Finally block always execute whether exception  handle or not  if any exception occurred before try block then finally block will not execute

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Yes  because no control statement can prevent finally from being executed   Here is a reference example  where all code blocks will be executed     x   Current result   Code   --- ---------------- ------ - - -                                                    public static int finallyTest       3                        int x   3                             try                                 try     4                                x      4   return 4                     return x                                   finally     3                                x--    3   throw                        throw new RuntimeException  Ahh                                                                   catch  RuntimeException e      4   return 4                 return   x                               finally     3                            x--                                                                                --- ---------------- ------ - - -       Result  4          In the variant below  return x  will be skipped  Result is still 4   public static int finallyTest         int x   3      try           try               x                if  true  throw new RuntimeException  Ahh                 return x     skipped           finally               x--                  catch  RuntimeException e            return   x        finally           x--            References  of course  track their status  This example returns a reference with value   4   static class IntRef   public int value    public static IntRef finallyTest         IntRef x   new IntRef        x value   3      try           return x        finally           x value       will be tracked even after return

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Also a return in finally will throw away any exception   http   jamesjava blogspot com 2006 03 dont-return-in-finally-clause html

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Yes  finally will be called after the execution of the try or catch code blocks   The only times finally won t be called are    If you invoke System exit   If you invoke Runtime getRuntime   halt exitStatus  If the JVM crashes first If the JVM reaches an infinite loop  or some other non-interruptable  non-terminating statement  in the try or catch block If the OS forcibly terminates the JVM process  e g   kill -9  lt pid gt  on UNIX If the host system dies  e g   power failure  hardware error  OS panic  et cetera If the finally block is going to be executed by a daemon thread and all other non-daemon threads exit before finally is called

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Because the final is always be called in whatever cases you have  You don t have exception  it is still called  catch exception  it is still called

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NOT ALWAYS  The Java Language specification describes how try-catch-finally and try-catch blocks work at 14 20 2 In no place it specifies that the finally block is always executed  But for all cases in which the try-catch-finally and try-finally blocks complete it does specify that before completion finally must be executed   try     CODE inside the try block   finally     FIN code inside finally block   NEXT code executed after the try-finally block  may be in a different method     The JLS does not guarantee that FIN is executed after CODE  The JLS guarantees that if CODE and NEXT are executed then FIN will always be executed after CODE and before NEXT   Why doesn t the JLS guarantee that the finally block is always executed after the try block  Because it is impossible  It is unlikely but possible that the JVM will be aborted  kill  crash  power off  just after completing the try block but before execution of the finally block  There is nothing the JLS can do to avoid this   Thus  any software which for their proper behaviour depends on finally blocks always being executed after their try blocks complete are bugged   return instructions in the try block are irrelevant to this issue  If execution reaches code after the try-catch-finally it is guaranteed that the finally block will have been executed before  with or without return instructions inside the try block

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Here are some conditions which can bypass a finally block    If the JVM exits while the try or catch code is being executed  then the finally block may not execute  More on sun tutorial   Normal Shutdown - this occurs either when the last non-daemon thread exits OR when Runtime exit    some good blog   When a thread exits  the JVM performs an inventory of running threads  and if the only threads that are left are daemon threads  it initiates an orderly shutdown  When the JVM halts  any remaining daemon threads are abandoned finally blocks are not executed  stacks are not unwound the JVM just exits  Daemon threads should be used sparingly few processing activities can be safely abandoned at any time with no cleanup  In particular  it is dangerous to use daemon threads for tasks that might perform any sort of I O  Daemon threads are best saved for  housekeeping  tasks  such as a background thread that periodically removes expired entries from an in-memory cache  source    Last non-daemon thread exits example     public class TestDaemon       private static Runnable runnable   new Runnable              Override         public void run                 try                   while  true                        System out println  Is alive                        Thread sleep 10                          throw new RuntimeException                                    catch  Throwable t                    t printStackTrace                  finally                   System out println  This will never be executed                                         public static void main String   args  throws InterruptedException           Thread daemon   new Thread runnable           daemon setDaemon true           daemon start            Thread sleep 100              daemon stop            System out println  Last non-daemon thread exits               Output     Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Is alive Last non-daemon thread exits  Is alive Is alive Is alive Is alive Is alive

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try-with-resoruce example  static class IamAutoCloseable implements AutoCloseable       private final String name      IamAutoCloseable String name            this name   name            public void close             System out println name             Test public void withResourceFinally         try  IamAutoCloseable closeable1   new IamAutoCloseable  closeable1             IamAutoCloseable closeable2   new IamAutoCloseable  closeable2              System out println  try          finally           System out println  finally              Test output   try closeable2 closeable1 finally

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finally block is executed always even if you put a return statement in the try block  The finally block will be executed before the return statement

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Concisely  in the official Java Documentation  Click here   it is written that -      If the JVM exits while the try or catch code is being executed  then   the finally block may not execute  Likewise  if the thread executing   the try or catch code is interrupted or killed  the finally block may   not execute even though the application as a whole continues

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Example code   public static void main String   args        System out println Test test        public static int test         try           return 0            finally           System out println  finally trumps return               Output   finally trumps return   0

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Also a return in finally will throw away any exception   http   jamesjava blogspot com 2006 03 dont-return-in-finally-clause html

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The finally block is always executed unless there is abnormal program termination  either resulting from a JVM crash or from a call to System exit 0    On top of that  any value returned from within the finally block will override the value returned prior to execution of the finally block  so be careful of checking all exit points when using try finally

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Same with the following code   static int f         while  true            try               return 1            finally               break                      return 2      f will return 2

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NOT ALWAYS  The Java Language specification describes how try-catch-finally and try-catch blocks work at 14 20 2 In no place it specifies that the finally block is always executed  But for all cases in which the try-catch-finally and try-finally blocks complete it does specify that before completion finally must be executed   try     CODE inside the try block   finally     FIN code inside finally block   NEXT code executed after the try-finally block  may be in a different method     The JLS does not guarantee that FIN is executed after CODE  The JLS guarantees that if CODE and NEXT are executed then FIN will always be executed after CODE and before NEXT   Why doesn t the JLS guarantee that the finally block is always executed after the try block  Because it is impossible  It is unlikely but possible that the JVM will be aborted  kill  crash  power off  just after completing the try block but before execution of the finally block  There is nothing the JLS can do to avoid this   Thus  any software which for their proper behaviour depends on finally blocks always being executed after their try blocks complete are bugged   return instructions in the try block are irrelevant to this issue  If execution reaches code after the try-catch-finally it is guaranteed that the finally block will have been executed before  with or without return instructions inside the try block

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finally will execute and that is for sure   finally will not execute in below cases    case 1    When you are executing System exit     case 2    When your JVM   Thread crashes   case 3     When your execution is stopped in between manually

[java] Does a finally block always get executed in Java?

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