Uncaught RuntimeException and finally clause: which comes first?

java try-catch-finally runtimeexception
chance picture chance · Nov 24, 2011 · Viewed 12.1k times · Source

A RuntimeException is thrown in try block without being caught, while the finally clause invokes System.exit().

public static void main(String[] args) {
    try {
        Integer.valueOf("NotANumber");
    } finally {
        System.out.println("finally");
        System.exit(0);
    }
}

The output is 

finally

If System.exit(0) is removed from finally, then the output is

finally
Exception in thread "main" java.lang.NumberFormatException: For input string: "NotANumber"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
    at java.lang.Integer.parseInt(Integer.java:449)
    at java.lang.Integer.valueOf(Integer.java:554)
    at exception.MyExcepTest.main(MyExcepTest.java:20)

Where "finally" may appears before, after or in between the meesage of NumberFormatException.

Can anybody explain it?

Answer

Thilo picture Thilo · Nov 24, 2011

The finally block will definitely be executed before the main method exits, and the stacktrace is printed by the JVM after that.

Maybe the stacktrace gets printed to System.err, and the two streams get mixed up in your console output in unpredictable ways (since they are produced basically simultaneously).

What happens when you print "finally" to System.err as well?

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