“unhandled checked exception as a thrown exception” in Java

Question

I'm learning chapter 5 of SCJP 6 Study Guide Exam_310-065 and in section Exception Declaration and the Public Interface it says

"Each method must either handle all checked exceptions by supplying a catch clause or list each unhandled checked exception as a thrown exception."

How do we list each unhandled checked exception as a thrown exception and how does it look like in the code? Thanks.

Answer 1

It looks like this:

public void foo() throws SomeCheckedException, AnotherCheckedException
{
    // This method would declare it in *its* throws clause
    methodWhichThrowsSomeCheckedException();

    if (someCondition)
    {
        // This time we're throwing the exception directly
        throw new AnotherCheckedException();
    }
}

See section 8.4.6 in the JLS for more information.

Answer 2

For instance, if you have:

public void doSomething() throws SomeException { 
    ... 
    throw new SomeException();
} 

And you want to invoke doSomething , you've got to either catch the exception, or declare the method using it as also susceptible of throwing SomeException , therefore propagating it further in the call stack:

public void doSomethingElse() throws SomeException { 
    doSomething();
}

Or

public void doSomethingElse() { 
    try { 
        doSomething();
    }
    catch (SomeException) { 
        // Error handling
    }
}

Take into account that RuntimeException s are not checked exceptions, so they are an exception to this rule.