Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract only method signature, no body. Interfaces specify what a class must do and not how. It is the blueprint of the class. An Interface is about capabilities like a Player may be an interface and any class implementing Player must be able to or must implement move. So it specifies a set of methods that the class has to implement.
Java - Abstraction - Tutorialspoint
Jakob Jenkov Last update: A Java abstract class is a class which cannot be instantiated, meaning you cannot create new instances of an abstract class. The purpose of an abstract class is to function as a base for subclasses. This Java abstract class tutorial explains how abstract classes are created in Java, what rules apply to them.
Java - Abstraction
Data abstraction is the process of hiding certain details and showing only essential information to the user. Abstraction can be achieved with either abstract classes or interfaces which you will learn more about in the next chapter. The abstract keyword is a non-access modifier, used for classes and methods: Abstract class: is a restricted class that cannot be used to create objects to access it, it must be inherited from another class. Abstract method: can only be used in an abstract class, and it does not have a body.
Methods are used to perform certain actions, and they are also known as functions. A method must be declared within a class. It is defined with the name of the method, followed by parentheses. Java provides some pre-defined methods, such as System.