What was the driving force to introduce default methods in Interfaces wef from Java 8 ?

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Q1. What was the driving force to introduce default methods in Interfaces wef from Java 8 ?

Ans. Earlier any class implementing an interface was supposed to implement all methods declared in an interface. There was no place for optionally implementing all or subset of methods.Though we have abstract classes wherein we could have provided such a mechanism by declaring some methods as abstract while providing definition for some. But as Abstract classes have a body and are comparatively heavier than interfaces and interfaces associate closely to the concept of providing interfacing than abstract classes, Java might have though of providing optional implementation for default methods. This way same interface can be reused in variety of ways rather than making copies of an interface to suit different needs.

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