Exception in super and sub class

Question

when super class method throws an exception then sub class overridden method can throws child exception but when we talk about constructor why we throws parent class exception in derived class constructor????

Answer 1

tcbhardwaj wrote:
     C() throws Throwable // why here parent of Exception class
     void ok() throws ArithmeticException // why here child of RunTimeException classFirst, you never need to declare a throws clause for unchecked exceptions--RuntimeException, Error, and their descendants.
However, there are a couple of general rules for checked exceptions (such as IOException, SQLException, etc.). As you're studying these, keep in mind that a throws clause is a contract that promises what the method will not do. In particular, it doesn't promise that the method will throw those exceptions. It promises that it will not throw any other checked exceptions not covered by that throws clause.
1. A child method that overrides a parent method cannot throw any checked exception outside what's covered by the parent's throws clause. So if the parent method declared throws IOException, the child cannot declare throws Exception, or throws SQLException, because both of those are outside the IOException "sub-hierarchy."
2. A child method that overrides a parent method can declare to throw less than the parent throws. This is because, if the parent promises not to throw outside of some set, and the child promises not throw outside of a subset of that set, then clearly he's also not throwing outside of the parent's set. If the parent method declares throws SQLException, IOException, then the child can declare no exceptions at all, or just SQLException, or just IOException, or any combination of any of the subclasses of SQLE and IOE.
Rules 1 and 2 do not apply in the case of constructors, because no constructor can ever override another constructor.
3. When any method or constructor, A, invokes any other method or constructor, B, then any checked exception declared to be thrown by B must be either caught or declared to be thrown by A. If A catches or throws a parent of an exception thrown by B, then he's also implicitly catching or throwing the one that B mentions.