Declarations, Initialization, and Scoping - SCJP Sun Certified Programmer for Java Platform SE6 - page 143

Does the following HouseCat class compile?
1. public class HouseCat extends Feline {
2. public void eat() {
3. System.out.println(“HouseCat is eating”);
4. }
5.
6. public void breathe() {
7. System.out.println(“HouseCat is breathing”);
8. }
9. }
Because HouseCat extends from Feline and Feline inherits the abstract walk method
from Mammal , HouseCat must either override walk or declare itself abstract . Because it does
neither, the class does not compile and generates the following error:
HouseCat.java:1: HouseCat is not abstract and does not override
abstract method walk() in Mammal
public class HouseCat extends Feline {
^
Declaring Interfaces
An interface is a collection of abstract methods. A class implements an interface, inheriting
all the abstract methods declared in the interface. Therefore, a class that implements an
interface must either override the interface methods or the class must be declared abstract .
An interface has the following properties:
An interface is defined in a .java file. If the interface is public , the name of the file
must match the name of the class. If the interface has the default access, it is only
accessible from within its package.
The bytecode file for a compiled interface is a .class file that matches the name of the
interface. All the rules of package names and subdirectories that apply to classes also
apply to interfaces.
All the methods in an interface are abstract, whether or not the abstract keyword is
explicitly denoted.
All the methods in an interface are public, whether or not they are explicitly declared public .
The fields of an interface are public , static , and final .
An interface cannot declare static methods.
An interface has some similarities to a class, but an interface is not a class. For example,
an interface cannot be instantiated, and it cannot contain any instance fi elds.