Inheritance - Beginning Java 8 Fundamentals - page 597

public class Q extends P {
public Employee getEmp() {
// code goes here
}
}
public class R extends P {
public Manager getEmp() {
// code goes here
}
}

Class P defines a getEmp() method that returns an object of Employee type. The getEmp() method of Class Q
overrides the getEmp() method of its superclass P because it has the same name, number of parameters (zero in this
case) of the same type in the same order, and the same return type, Employee . The getEmp() method of class R also
overrides the getEmp() method of class P even though its return type Manager is different from the return type of the
overridden method, which is Employee . The getEmp() method of class R overrides its superclass getEmp() method
because an instance of Manager type can always be assigned to a variable of Employee type without any typecast.

Method Overriding Rule #5
The access level of the overriding method must be at least the same or more relaxed than that of the overridden
method. The three access levels are public , protected and package-level that allow for inheritance. Recall that
private members are not inherited and hence cannot be overridden. The order of access level from the most
relaxed to the strictest is public , protected , and package-level. If the overridden method has public access level,
the overriding method must have the public access level because public is the most relaxed access level. If the
overridden method has protected access level, the overriding method may have public or protected access level.
If the overridden method has package-level access, the overriding method may have public , protected , or package-
level access. Table 16-1 summarizes this rule. I will discuss why this rule exists shortly.

Table 16-1. List of Allowed Access Levels for an Overriding Method

Overridden Method Access Level Allowed Overriding Method Access Level

public public

protected public, protected

package-level public, protected, package-level

Method Overriding Rule #6
A method may include a list of checked exceptions in its throws clause. Although it is allowed to include an unchecked
exception in the throws clause of a method, it is not required. In this section, I am discussing only checked exceptions.
The overriding method cannot add a new exception to the list of exceptions in the overridden method. It may remove
one or all exceptions or it may replace an exception with another exception, which is one of the descendants of the
exception listed in the overridden method. Let's consider the following class definitions:

public class G {
public void m1() throws CheckedException1, CheckedException2 {
// Code goes here
}
}