Thread: keywords

Extends can be used in two different contexts: an interface extending another interface, or a class extending another class. Implements can only be use in the context of a class implementing an interface. An interface can never extend/implement a class, and a class can never extend an interface. Classes are allowed to implement multiple interfaces but can only extend one class. Interfaces can extend any number of interfaces they want to.

Syntaxes:

public class BaseClass
{}
 
public interface BaseInterface
{}
 
public class ClassA extends BaseClass
{}
 
public class ClassB implements BaseInterface
{}
 
public interface InterfaceA extends BaseInterface
{}
 
public interface InterfaceB
{}
 
public class ClassB implements InterfaceA, InterfaceB
{}
 
public interface InterfaceC extends InterfaceA, InterfaceB
{}