Inheritance - Beginning Java 8 Fundamentals - page 598

If a class overrides m1() method of class G , it must not add any new checked exception to it. The following code
will not compile, because it has added a new checked exception CheckException3 in the overridden method m1() :
public class H extends G {
public void m1() throws CheckedException1, CheckedException2, CheckedException3 {
// Code goes here
}
}
The following class declarations override the m1() method in class G and they are all valid. In class I , the
method m1() removes both exceptions. In class J , it removes one exception and keeps one. In class K , it keeps one
and replaces the other one with a descendant type assuming that the CheckedException22 is a descendant class of
CheckedException2 .
public class I extends G {
// m1() removes all exceptions
public void m1() throws {
// Code goes here
}
}
public class J extends G {
// m1() removes one exception and keeps one
public void m1() throws CheckedException1 {
// Code goes here
}
}
public class J extends G {
// m1() removes keep one and replaces one with a subclass
public void m1() throws CheckedException1, CheckedException22 {
// Code goes here
}
}
The rules about the return type and the list of exceptions of an overriding method may not be obvious. I will
discuss the reasons behind these rules. There is a reason behind these rules, which is “A variable of a class type can
hold the reference of an object of any of its descendants.” When you write code using the superclass type, that code
must also work without any modification with objects of subclass types. Let's consider the following definition of class
P assuming the EmpNotFoundException is a checked exception class:
public class P {
public Employee getEmp(int empId) throws EmpNotFoundException {
// code goes here
}
}