The Java Language Specification, Third Edition

8.4.8 Inheritance, Overriding, and Hiding CLASSES
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Note that it is possible for a method to have a declared return type and yet
contain no return statements. Here is one example:
class DizzyDean {
int pitch() { throw new RuntimeException("90 mph?!"); }
}
8.4.8 Inheritance, Overriding, and Hiding
A class C inherits from its direct superclass and direct superinterfaces all non-private
methods (whether abstract or not) of the superclass and superinterfaces
that are public, protected or declared with default access in the same package as C
and are neither overridden (§8.4.8.1) nor hidden (§8.4.8.2) by a declaration in the
class.
8.4.8.1 Overriding (by Instance Methods)
An instance method m1 declared in a class C overrides another instance method,
m2, declared in class A iff all of the following are true:
1. C is a subclass of A.
2. The signature of m1 is a subsignature (§8.4.2) of the signature of m2.
3. Either
◆ m2 is public, protected or declared with default access in the same package
as C, or
◆ m1 overrides a method m3, m3 distinct from m1, m3 distinct from m2, such
that m3 overrides m2.
Moreover, if m1 is not abstract, then m1 is said to implement any and all declarations
of abstract methods that it overrides.
DISCUSSION
DRAFT
The signature of an overriding method may differ from the overridden one if a formal
parameter in one of the methods has raw type, while the corresponding parameter in the
other has a parameterized type.
The rules allow the signature of the overriding method to differ from the overridden
one, to accommodate migration of pre-existing code to take advantage of genericity. See
section §8.4.2 for further analysis.