Alex Rivera | Logout

Does a finally block always get executed in Java?

Asked 2008-09-15T17:43:54.513
2714

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");
}
java error-handling return try-catch-finally
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3 Answers

431

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.

answered 2008-09-15T18:19:53.507
12

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.

answered 2010-05-13T06:18:23.697
7

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.

answered 2008-10-01T15:15:44.153

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