Question

I have gone through this interview
http://www.artima.com/intv/handcuffs.html
and some article and discussion about checked exception. That said checked exception is untried experiment to bring in java. It can bring versionability and scalability issues. Bruce eckel also provide a adapter to convert checked exception to unchecked exception to avoid called force to catch exception. I also heart hibernate move from checked exception to unchecked exception. I wonder what if we remove checked exception mechanism? I also agree that checked exception is not necessary existed.

Answer 1

Not a lot would happen, actually. On the VM level, all exceptions are unchecked. You can verify this by doing e.g. the following:

public class A {
    public static void a() {
        /* Do nothing */
    }
}

public class B {
    public static void main(String[] args) {
        A.a();
    }
}

Store these classes in their respective files A.java and B.java and compile them. Then, change A to the following:

public class A {
    public static void a() throws Exception {
        throw(new Exception("foo"));
    }
}

Recompile A.java without recompiling B.java. Then run B, and you’ll see the thrown exception from A propagating and terminating the program as if it were a RuntimeException, without the VM complaining of linkage errors or anything.

Checked exceptions are merely a syntax-level feature of the Java language. Removing it wouldn’t affect the VM implementation or even the language model one bit.