Page 222 - AP Computer Science A, 7th edition

all the non-default (i.e., abstract) methods declared in the interface. If it fails to implement any of the methods, the class must be declared abstract.
Defining an Interface
An interface is declared with the interface keyword. For example,
public interface FlyingObject {
void fly(); //method that simulates flight of object
boolean isFlying(); //true if object is in flight,
//false otherwise
The implements Keyword
Interfaces are implemented using the implements keyword. For
example,
public class Bird implements FlyingObject {
...
This declaration means that two of the methods in the Bird class must be fly and isFlying. Note that any subclass of Bird will automatically implement the interface FlyingObject, since fly and isFlying will be inherited by the subclass.
A class that extends a superclass can also directly implement an interface. For example,
A nonabstract class that implements an interface must implement every abstract method of the interface.
public class Mosquito extends Insect implements