CLASSES

 a class is a blueprint from which individual objects are created

What do Java classes contain?

A class in Java can contain:

  • Data Member
  • Method
  • Constructor
  • Block
  • Class
  • Interface

In the real world, you'll often find many individual objects all of the same kind. There may be thousands of other bicycles in existence, all of the same make and model. Each bicycle was built from the same set of blueprints and therefore contains the same components. In object-oriented terms, we say that your bicycle is an instance of the class of objects known as bicycles. A class is a blueprint from which individual objects are created.

The following Bicycle class is one possible implementation of a bicycle:

  1. class Bicycle { 
  2. int cadence = 0; 
  3. int speed = 0; 
  4. int gear = 1; 
  5.   void changeCadence(int newValue) { 
  6. cadence = newValue; 
  7. } 
  8.   void changeGear(int newValue) { 
  9. gear = newValue; 
  10. } 
  11.   void speedUp(int increment) { 
  12. speed = speed + increment;  
  13. } 
  14.   void applyBrakes(int decrement) { 
  15. speed = speed - decrement; 
  16. } 
  17.   void printStates() { 
  18. System.out.println("cadence:" + 
  19. cadence + " speed:" +  
  20. speed + " gear:" + gear); 
  21. } 
  22. } 

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