Java Network Programming Research Topic Presentation Java Interfaces

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Java Network ProgrammingResearch Topic
PresentationJava Interfaces

• Abbu Rajaram Rakesh Kumar
• rakesh.abbu-rajaram_at_sunderland.ac.uk

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Java Interfaces Introduction

• An interface defines a protocol of behaviour that
  can be implemented by any class anywhere in the
  class hierarchy.
• Definition An interface is a named collection of
  method definitions (without implementations). An
  interface can also declare constants.
• When a method is called from one class to
  another, both the classes should be present at
  compile time for the verification of the
  signatures, thus as the class hierarchy gets high
  performance deteoriates. Interfaces are designed
  to avoid such a problem.

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Java Interfaces Contd..

• Structure similar to a class, but lack instance
  variables.
• It is a simple list of unimplemented methods.
• A class can be fully abstract by implementing
  interfaces.
• The interfaces only define methods but not, what
  they do.
• Any number of classes can implement a single
  interface.
• A class can implement any number of interfaces.
• They are designed to support dynamic method
  resolution at run time.
• Interfaces do not follow hierarchy as the classes
  do.

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Class Vs Interfaces

• Interface does not implement any methods unlike
  an abstract classes.
• A class can implement many interfaces but can
  have only one super class.
• Many classes from different hierarchy can
  implement interfaces.

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Define Implement Interfaces

• Defined similar to class, uses interface
  keyword.
• The access type is either abstract or public
  but never private.
• Methods are declared but no bodies of the method
  are specified.
• An example below
• public interface CallBack
• int x, y 0
• string a yes
• string b no
• void callback(int p)

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Define Implement contd..

• Variables can be defined in the interfaces but
  they are done implicitly final and static.
• The interface methods are declared as public
  access.
• Class implementing one or many interfaces, writes
  the method codes of all the interfaces in the
  class body.
• The class can write additional methods in
  addition to the interface methods.
• The instance object of the class implementing the
  interface can also call the interface methods
  variables.
• The method called is looked up dynamically at run
  time,

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Define Implement contd..

• here the classes are created later than the code
  which call them.
• Calling code can dispatch thru interface, without
  having to know about the callee.
• Be cautious while using because it requires lot
  of processing capability, because of its run time
  lookup.
• An interface can inherit another interface.
• Class implementing the interface can also do
  partially, then such a class and its inheriting
  class should be declared abstract.
• Interface can be used to declare a variable of
  its type.

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Applying Interfaces

• Interface is a powerful tool, interface methods
  can be defined accordingly in the different
  implementing classes.
• The called methods are invoked at the run time
  rather than at the compile time.
• Thus run time polymorphism is achieved.

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References

• Herbert Schildt (2002), The Complete Reference,
  Java 2. Fifth Edition, Tata McGraw-Hill, India.
• http//java.sun.com/docs/books/tutorial/java/inter
  pack/interfaces.html