Java™ How To Program (Early Objects), Tenth Edition

Section 10.9 Creating and Using Interfaces

• An interface (p. 421) specifies what operations are allowed but not how they’re performed.

• A Java interface describes a set of methods that can be called on an object.

• An interface declaration begins with the keyword interface (p. 421).

• All interface members must be public, and interfaces may not specify any implementation details, such as concrete method declarations and instance variables.

• All methods declared in an interface are implicitly public abstract methods and all fields are implicitly public, static and final.

• To use an interface, a concrete class must specify that it implements (p. 421) the interface and must declare each interface method with the signature specified in the interface ...