Question

Well here I’ve seen this in API and other related questions:

try {

} catch (IOException e) {
    throw new SampleException("Other IOException", e);
}

Which calls a new exception.

But now I have seen this example which calls itself. I’m trying to write the documentation and it seems it calls itself again.

try {
    statements;
}catch(TheException e) {
    //perform operations before exits;
    throw e; 
}

Re-throwing the exception so that other handlers get a chance to
process the exception

I guess we can not add one more TheException after our catch exception! So in this case who is the other handler? I tested it and I realize even codes after catch clause are not compiled!

Answer 1

Let’s say you have two methods.

First one:

public void methodA() throws IOException {

    try {

        // methodWhichCanThrowIOException();

    } catch (IOException e) {

        // //perform operations before exits;
        throw e;
    }
}

Second one:

public void methodB() {

    try {

        methodA();

    } catch (IOException e) {

        // //perform operations;
    }
}

See how method B calls method A. The exception raised originally inside method A is handler by method A itself, but once this is done, method A decides to throw the exception so other handlers get a chance to process the exception. Other hander as method A. Notice that method A can be in a different class, in a different layer.

For method A, throwing an exception is a nice way to inform method B that something happened.