Inheritance topic

INHERITANCE IN JAVA

INHERITANCE IS THE TECHNIQUE OF EXTENSION OF ALREADY EXISTING CLASS. IT MEANS WE CAN PRODUCE NEW CLASS FROM EXISTING CLASS . IN THIS PROCESS, EXISTING CLASS IS CALLED AS SUPER CLASS / BASE CLASS  AND THE EXTENDED CLASS IS CALLED AS SUB CLASS / DERIVED CLASS / NEW CLASS. SUB CLASS IS 

POWERFUL THAN SUPER CLASS, BECAUSE SUB CLASS HAVE ALL THE FEATURES OF SUPER CLASS AND ADDITIONAL FEATURES OF ITSELF. THE MAIN ADVANTAGE OF INHERITANCE IS REUSABILITY OF CODE. IF WE CREATE AN OBJECT TO SUB CLASS IT CONTAINS A COPY OF SUPER CLASS OBJECT. THAT IS THE REASON WHY SUPER CLASS MEMBERS ARE AVAILABLE TO SUB CLASS. GENERALLY WE DON'T CREATE AN OBJECT TO SUPER CLASS IN INHERITANCE. SO BETTER WAY IS CREATE OBJECT TO SUB CLASS NOT TO SUPER CLASS.

           TYPES OF INHERITANCE

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            1) SINGLE INHERITANCE

            2) MULTI LEVEL INHERITANCE

            3) HIERARCHICAL INHERITANCE

            4) MULTIPLE INHERITANCE

            5) HYBRID INHERITANCE

JAVA'S RULE IS THAT A CLASS CAN HAVE ONLY ONE SUPER CLASS. SO JAVA DOES NOT SUPPORT MULTIPLE, MULTI PATH AND HYBRID INHERITANCES DIRECTLY.

1)    SINGLE INHERITANCE
   
       DERIVING NEW CLASS FROM SINGLE CLASS.
2)    MULTILEVEL INHERITANCE
     
       DERIVING NEW CLASS FROM ANOTHER DERIVED CLASS.
3)   HIERARCHICAL INHERITANCE

      THIS TYPE OF INHERITANCE IS SIMILAR TO A TREE. IN THIS MODEL EACH SUPER         CLASS HAS MINIMUM TWO SUB CLASSES. GENERALLY IN THIS MODEL OBJECTS           ARE CREATED FROM LEAF NODE (LAST SUB) CLASSES.

          MULTIPLE INHERITANCE  & HYBRID ARE NOT PREFERED.