catching exception in catch block

Question

What is difference between

try {
    ...
} catch (Nullpointerexception e) { ... }
} catch (Exception e) { ... }

and

try {
    ...
} catch (Exception e) { ... }

Suppose I have a NullPointerException, which one is best? And why?

`Exception` is very general and `NullPointerException` is specific to a `null` object you're trying to get an attribute or access a method. It's better to `catch` your specific exception (in the case `NullPointerException`), otherwise you might hide some problems in your code that should be fixed when catching a general exception. — Tom, Nov 20 '16 at 09:33

score 2 · Answer 1 · edited May 23 '17 at 10:33

Q: What is difference between catch(Nullpointerexception e) and catch(Exception e)?

A: The one former is specific, the latter is general.

There are times when you want to handle specific classes of exceptions (like "NullPointerException") one way, but different classes of exception (like "IOException") differently.

In general, you should should choose to handle the "narrowest" exception possible, rather than "handle everything".

Another significant difference between "NullPointerException" (and "ArrayIndexOutOfBound") vs. many other exceptions is that NullPointerException is an unchecked exception.

Note, too, that in Java 7 you can how catch multiple different exceptions in the same catch block:

Catching Multiple Exceptions in Java 7

// Pre-Java 7 code:
try {

    // execute code that may throw 1 of the 3 exceptions below.

} catch(SQLException e) {
    logger.log(e);

} catch(IOException e) {
    logger.log(e);

} catch(Exception e) {
    logger.severe(e);
}

But now...

// Java 7 and higher
try {

    // execute code that may throw 1 of the 3 exceptions below.

} catch(SQLException | IOException e) {
    logger.log(e);

} catch(Exception e) {
    logger.severe(e);
}

manfcas · Answer 2 · 2016-11-26T11:17:18.620

You should use the second option if the code to handle Exception is always the same, and the first one if you want different behaviours for different Exceptions.

In any case, is very rare to need a catch clause for NullPointerExceptions, because you can simply avoid them with a null check in your code (you'll really need a catch clause only if the NullPointerException is generated in code you cannot control, for example in the internals of a library).

Starting from Java 7, you can even do:

try {
    ...
} catch (NullPointerException | AnotherException e) {
    ...
}

to avoid replicating the same body for different Exception classes.

Prior to Java 7, you have to include the Exception handling code in a method and call if from multiple catch clauses to avoid its replication.

catching exception in catch block

2 Answers2