Abstract Class Extending Concrete Class

But when u extend a concrete class by a astract class what possible use it can be of. Concrete class in java. Similar to interfaces but 1 can implement methods 2 fields can have various access modifiers and 3 subclasses can only extend one abstract class.

They cannot have any unimplemented methods.

Abstract class extending concrete class. Subclasses extending an abstract class may implement these inherited abstract methods. If the child class implements all such abstract methods it becomes a concrete class. It is a complete class and can be instantiated. The classes that extend the abstract class can override the methods depending on its needs.

A concrete class is a class that has an implementation for all of its methods. As abstract classes can have both abstract and non abstract methods hence the abstract modifier is necessary here unlike in interface where only abstract methods are allowed. Abstract method bodies must be empty no curly braces subclasses must implement the abstract classs abstract methods. Is it possible if yes whether its a good approach in point.

I have an abstract class. What i meant by polymorphism was abstract classes are extended by concrete class to override the methods present in them. So overriding holds the key here. I want to extend the abstract class by another abstract class and then implement the extended abstract class.

But if it does not the child class also becomes an abstract class. Other classes extend abstract classes. It can also extend an abstract class or implement an interface as long as it implements all their methods. Can have both abstract and concrete methods.