Invariant that ensures that no method throws an exception other than PreconditionError or InvariantError

Question

I want to add two conditions in Invariant:

1. All Natural methods must guarantee (via PreconditionErrors or InvariantErrors) that operations resulting in an overflow are blocked
2. Ensure that no method throws an exception other than PreconditionError or InvariantError.

Following is my code so far for the implementation. I am new to these java contracts so struggling to make it through.

//Add an invariant here.
@Invariant({
    "data >= 0",
    "data <= Integer.MAX_VALUE",
    "noUnexpectedExceptions()"    
})
public class Natural implements Comparable<Natural> {
    private int data;
    private boolean noUnexpectedExceptions() {
        try {
            assert true;
            return true;
        } catch (PreconditionError | InvariantError e) {
            return true;
        } catch (Throwable t) {
            return false;
        }
    }
    
    public void increment() {
        data++;
    }

    public void decrement() {
        data--;
    }
}