Java Programming/Keywords/abstract

abstract is a Java keyword. ... It declares a class abstract, not all its methods are defined/implemented. Objects are not normally created from an abstract class. Rather, they are created from either a non-abstract subclass, or by having the functions declared alongside a new statement (which is not recommended).

It also declares a method abstract, that is, not implemented in the abstract class. A method cannot be declared abstract in a non abstract class.

Syntact:

public abstract class ClassName
or
abstract public class ClassName

and for methods in an abstract class :

public abstract void methodName();  // --- No body, no implementation ---
or
abstract public void methodName();  // --- No body, no implementation ---

For example:

public abstract ClassName { // --- This method does not have a body; it is abstract. --- public abstract void abstractMethod(); // --- This method does have a body; it is implemented in the abstract class and gives a default behavior. --- public void normalMethod() { ... } }