Catch separate exceptions or use instanceof - Java 6

Question

Assume that this piece of code is in 20 places and always the same

try {
    // do something
} catch (FirstException e) {
    // log it
} catch (SecondException e) {
    // log it
}

Wouldn't be better to use something like this or instanceof is not good solution?

try {
    // do something
} catch(Exception e) {
    logException(e);
}

void logException(Exception e) {
    if (e instanceof FirstException) {
        // log it
    } else if (e instanceof SecondException) {
        // log it differently
    } else {
        // do something with other exception 
    }
}

The only thing that I really hate about the solution is catching Exception which is definitelly not the best way... Is there any better way?

Answer 1

1. In Java 7, use catch (FirstException1 | SecondException | ...)
2. There may be nothing wrong with catch (Exception e)—you do want to log all exceptions, don't you? I would in fact advise catch (Throwable t) because OutOfMemoryError s and StackOverflowErrors also want to be logged.

An advice from many years of experience with logging exceptions is to log them all the same way. The exception message is enough as human-readable text, and what the developer really needs for debugging is the stack trace.

Just be careful about one thing: never catch exceptions too early: catch them at a single place for the whole application, the so-called exception barrier—it is at the level where you enter and exit a unit of work.

If checked exceptions are giving you trouble at the lower level, wrap them into RuntimeException:

try {
  ...
} 
catch (RuntimeException e) {throw e;} 
catch (Exception e) {throw new RuntimeException(e);}

Only if you know precisely and in advance that there is an exception which has business-level meaning to your application, and will not abort the current unit of work, but redirect its flow, is it appropriate to catch that exception at a lower level. In practice such exceptions are rare compared to the totality of all possible exceptions thrown by the application code.

Answer 2

The first approach is definitely better. Generally it is a bad practice to catch Exception because in this case you catch RuntimeExceptions too.