can abstract class implement interface code example

Example 1: is it necessary for abstract class to have abstract method

No, abstract class can have zero abstract methods.

Example 2: abstract classes and interfaces in java

abstract class have no implementation of methods functions inside it. the classes which extending abstract class have to implement it

Example 3: can abstract class have implementation java

abstract classes have no implementation of functions methods inside it which declared as abstract methods. classes which are inheriting it have to overriden it. and final absract class can not be overriden