The same modifier appears more than once in an interface declaration.Įvery interface is implicitly abstract. The access modifier public is discussed in §6.6. Names see §8.1.1 for an example involving classes.Īn interface declaration may be preceded by interface modifiers: This is the same scoping rule as for class type
The Identifier specifies the name of the interface and has as its scope the entire Interface Point Ī compile-time error occurs because a class and an interface in the same package The compilation unit containing the interface declaration. A compile-time errorĪlso occurs if the Identifier naming an interface appears as the name by which aĬlass or interface is to be known via a single-type-import declaration (§7.5.1) in Name of any other class or interface in the same package. InterfaceModifiers opt interface IdentifierĪ compile-time error occurs if the Identifier naming an interface appears as the It is not sufficient that the class happen to implement all the abstract methods of the interface the class or one of its superclasses must actually be declared to implement the interface, or else the class is not considered to implement the interface.Īn interface declaration specifies a new reference type: This (multiple) interface inheritance allows objects to support (multiple) common behaviors without sharing any implementation.Ī variable whose declared type is an interface type may have as its value a reference to any object that is an instance of a class declared to implement the specified interface. A class necessarily implements all the interfaces that its direct superclasses and direct superinterfaces do. Java programs can use interfaces to make it unnecessary for related classes to share a common abstract superclass or to add methods to Object.Īn interface may be declared to be an direct extension of one or more other interfaces, meaning that it implicitly specifies all the abstract methods and constants of the interfaces it extends, except for any constants that it may hide.Ī class may be declared to directly implement one or more interfaces, meaning that any instance of the class implements all the abstract methods specified by the interface or interfaces. Unrelated classes can implement it by providing implementations for its abstract This type has no implementation, but otherwise * What Is an Interface in Java? Beginners Guide to Java Interface.Interfaces Contents | Prev | Next | IndexĪn interface declaration introduces a new reference type whose members areĬonstants and abstract methods.
JAVA INTERFACE HOW TO
We normally prefer interface in real time when we know what to do but don’t know how to do. An interface cannot contain instance fields.