Is there possibility that a finally block might not execute?

Question

We know that no matter whether an exception is thrown, or caught and handled it, the finally block will get executed, So I was curious that is there any possibility that finally block will not executed.

And if System.exit() is called either in try or catch, then also will the finally gets called?

If you pull out the plug of your pc, the finally block will not get executed. — Fortega, Mar 10 '10 at 15:28

score 25 · Accepted Answer · answered Mar 10 '10 at 15:13

25

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.

Source: java.sun.com: Java Tutorial: The finally Block

answered Mar 10 '10 at 15:13

Daniel Vassallo

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take note of the "may" word there. – setzamora Mar 10 '10 at 15:24

score 6 · Answer 2 · answered Mar 10 '10 at 15:14

6

System.exit() will prevent a finally block from executing.

answered Mar 10 '10 at 15:14

msw

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score 3 · Answer 3 · answered Mar 10 '10 at 15:13

In the Java documentation:

http://java.sun.com/docs/books/tutorial/essential/exceptions/finally.html

It explains Finally very well.

They do note that if the JVM exits, that the finally block will not be called. Or if a thread that is running the block of code gets killed, the finally block will not be called. In all other cases it will.

score 3 · Answer 4 · answered Mar 10 '10 at 15:14

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One thing I can think of right now is an OutOfMemoryError in which case there is a chance that no further code in your app can be executed.

answered Mar 10 '10 at 15:14

alex.zherdev

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Even in case of an OutOfMemoryError, the finally block will be executed. The execution of the finally block itself may then of course cause an OutOfMemoryError itself, but that may also happen, even if the try block completed succesfully. – jarnbjo Mar 10 '10 at 15:56

score 3 · Answer 5 · edited Mar 12 '10 at 16:31

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try {
    System.out.println("BEFORE");
    System.exit(0);
    System.out.println("AFTER");
} finally {
    System.out.println("FINALLY");
}

this will give you the output:

BEFORE

edited Mar 12 '10 at 16:31

Daniel Vassallo

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answered Mar 10 '10 at 15:25

setzamora

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score 1 · Answer 6 · answered Mar 10 '10 at 15:25

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System.exit(1); you can use

answered Mar 10 '10 at 15:25

giri

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score 1 · Answer 7 · answered Dec 23 '20 at 08:58

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Another situation that I can think of (that is left out from the other answers) is when an exception is thrown inside a finally block, in that case the finally block will not be "completely" executed.

answered Dec 23 '20 at 08:58

Aaditya Sharma

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score 0 · Answer 8 · answered Mar 10 '10 at 15:23

If some Java Native Interface method segfaults (a library function outside of java but called from there crashes) a finally method will also not be called because the entire JVM stops.

Errors in the JVM itself also result in a crash and prevent everything from continued execution.

score 0 · Answer 9 · edited Sep 19 '15 at 10:47

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the finally clause in the try-catch exception block always executes, irrespective of the occurrence of exception in the normal java program flow. If the execution flow is stopped before the finally clause then the finally block will not be executed.

we can use System.exit(1); before finally block and stop the execution flow of the program.

edited Sep 19 '15 at 10:47

Gilles

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answered Sep 19 '15 at 09:42

Prashant Lokhande

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Is there possibility that a finally block might not execute?

9 Answers9