20+ Differences between Abstract Class and Interface

Abstraction is the technique of providing end users with just the functionality of a feature rather than specifying how the quality is really implemented on the back end.

This is referred to as “presenting simply the functionality of a feature.” namely, its purpose, the activities it engages in, and how it operates (hiding).

Interfaces and abstract classes are necessary for the abstraction process because they serve the same overarching function.

Comparison Between Abstract Class And Interface

ParameterAbstract ClassInterface
DefinitionThere are no permissions switches or other editable controls in the UI. Unless a private modifier is included explicitly in the specification, the default assumption is that an interface definition is open to the public. This applies to all of them.Many Java novices struggle to understand interfaces. Interfaces can’t be used to define methods, confusing inexperienced programmers. Instead, they’re used for declaration. Interface methods must be abstract. With Java 8’s lambda expressions, interfaces may contain one non-abstract method.
ModifiersAbstract Classes can have access modifiers added if the programmer desires. They have access to this capability. The functionality is available for the developer to use at their discretion and is made available to them.There are no permissions switches or other editable controls in the UI. Unless a private modifier is specifically included in the specification, the default assumption is that an interface definition is open to the public. This applies to all of them.
ImplementationWhen dealing with an Abstract Class, you could find that you are forced to rely on the implementation the class provides by default. This is because you do not have a choice in the matter.If you attempt to locate all of the implementors of the interface and add newly defined features simultaneously, the interface extension process might become a living nightmare for you. This is a process that may take a significant amount of time.
UsageIt is acceptable to use whatever it is that several instances of the same type implement in a way that results in the same behavior as a consequence. When this occurs, it is legal to use whatever it is.Utilizing an interface is the most efficient way to utilize it when the only component that must remain consistent across many implementations is the method signature. There is room for more than one value hierarchy; each must include types that may take several forms.
KeywordIf you want a method in an abstract class to be deemed abstract, you must ensure that the term “abstract” is used in the definition of the method. Otherwise, the method won’t be considered abstract. This is a must.The keyword is unnecessary to define abstract methods included in an abstract interface. This is because it is not required, as well as the fact that it is not required. This is because doing so is not required in any way.

What Is The Difference Between Abstract Class And Interface?

What exactly is Abstract Class?

Only classes whose declarations use the abstract keyword are considered abstract. Zero or more abstract methods must be present in abstract classes. In other words, procedures devoid of a physical form.

There may be a few different ways to implement it. Building concrete classes from abstract ones is facilitated by abstract classes.

The inheriting class is responsible for implementing the abstract method. Classes that are considered abstract are not capable of being instantiated.

🔑 Key Difference: Abstract Class

  • An abstract class can have members who do not adhere to the abstract or non-abstract tenets of the course. 
  • Because abstract classes do not support multiple inheritances, it is not suggested that you use them in your projects.
  • In its composition, an abstract class may include final or non-final variables, static or non-static variables, and non-static variables.
  • Under certain conditions, using abstract classes enables one to implement a specified interface.
  • It is mandatory to use the abstract keyword if a class is designed to have no concrete implementation. Abstract classes do not have a concrete implementation.
  • It is not feasible for an abstract Java class to support multiple Java interfaces and extend another Java class; this combination of capabilities is not exclusive to Java classes.
  • You can construct an extension of an abstract class you are working with using the “extends” keyword in your programming.
  • An abstract Java class can include members with the access level set to private, protected, or others.
Features Of Abstract Class

What exactly is Interface?

An implementation of a class may be crafted from its interface. No actual methods are given in the interface (methods that have code).

All of the operations available via an interface are considered abstract methods. It is not possible to instantiate an interface. On the other hand, classes may be instantiated if they implement the appropriate interface.

The only variable that may exist in an interface and is not an instance variable is a public static final variable (i.e., constant class variables).

🔑 Key Difference: Interface

  • You are only permitted to have access to abstract methods when you are really inside of an interface. 
  • Beginning right now, you will have the capability of writing methods in Java 8 that are both static and default, and you will have access to both.
  • The inheritance of many interfaces simultaneously is not an impossible task. No dynamic or temporary variables are included inside the interface itself at this time.
  • In no way, shape, or form is it possible to put an abstract class into action using its corresponding interface.
  • Before declaring an interface, using the “interface” keyword in every relevant context is required.
  • It can expand upon a currently-used Java interface only through a distinct Java interface.
  • A procedure that makes it possible to “implement” an interface is referred to as having the term “implements” in its name.
  • The assumption that all members of a Java interface are accessible to the general public is made using the default settings.
Features Of Interface

Contrast Between Abstract Class And Interface


  • Abstract Class – If the abstract keyword is included in the declaration of a class, then that class will be understood to be an abstract one.

    Abstraction requires that a class contain at least one abstract method; without such a method, the class in question cannot be described as abstract.

    A single abstract class could, in fact, comprise a significant number of concrete method implementations.
  • Interface – The process of putting a class into action may include the usage of an interface, which may be thought of as a form of blueprint.

    Each one of the methods that are included inside the interface itself is considered to be an abstraction. The user interface does not provide access to any actual methods in any way.


  • Abstract Class – Whenever a declaration of an abstract class is formed, the use of the abstract keyword is a requirement that must be met. It is not possible to instantiate abstract classes.

    The “extends” keyword makes designing subclasses derived from the abstract class possible. These subclasses may be accessed via the parent class. It is possible to build these subclasses.
  • Interface – If you comment on an interface using the term “interface,” you will obtain more particular results from your comment.

    It is probable that the term “implies” will prove to be a beneficial phrase when referring to the process of putting an interface into action. This is because “implies” connotes the idea that something is the case.


  • Abstract Class – When formulating your overall plan, be sure to include concepts that are both particular and general.

    Candidates who have a probability of being deemed appropriate for the application while it is going through the process of producing a default approach Candidates who have a chance of being considered suitable for the application
  • Interface – Although Java 8 introduces support for static and default methods in addition to abstract methods, the only methods that may be included are abstract methods. It does not permit submitting any other process form as there is no room for them.

    We cannot have it since this severely restricts our ability to implement it; as interfaces can only give abstraction, we cannot. We cannot have stereotypes since interfaces only supply it in a limited form.


  • Abstract Class – If you need a base class or if numerous implementations of the same type have the same behavior, you must use this. Use of this is required.

    Because you do not have a say in the issue, there is no way for you to affect the final result of the scenario as you do not have a choice in the matter.
  • Interface – It is an excellent solution for situations in which the signature of a method is the only component that stays constant across many implementations.

    In other words, it is a solution suitable for the circumstances. You also need to care about this element of the issue if one of your classes needs dependency injection or different behavior.


  • Abstract Class – No instance of an abstract class may be created. For example, an abstract class may have a set of abstract methods that a concrete subclass must define. It is possible to extend one abstract class from another.

    When implementing an abstract class, a class may only extend for a single abstract class instead of many interfaces. However, unlike interfaces, abstract classes may include final and non-final methods and private and protected properties.
  • Interface – We are unable to instantiate an interface. The public access qualifier is not required since all interface methods are considered public by default.

    All methods specified inside a Java interface before Java 8 had to be abstract, meaning they couldn’t contain a body.

    On the other hand, as of Java 8, an interface may contain both default and static methods, the bodies of which can be specified. By convention, interface fields are all public, static, and final.

Example Of Abstract Class And Interface

Example of an Abstract Class

The qualities listed below can be used to define an abstract class called “Animal”:

  • It stores the animal’s name in a protected member variable dubbed “name.”
  • Its “make sound ()” abstract method describes the sound the animal creates.
  • The word “getName()” is a concrete method that returns the animal’s name.
  • The concrete animal classes “Dog” and “Cat” are derived from it because they cannot be created independently.

Example of an Interface

The following attributes can be used to define an interface with the name “Drawable”:

  • The two methods, “draw()” and “setColor(),” are declared.
  • The “draw()” method represents the painting of the interface-implementing object.
  • Setting an object’s color is represented by the “setColor()” method.
  • Both methods must be implemented by any class that adheres to the “Drawable” interface.
  • There are no variables or specific behaviors in the interface.
Abstract Class And Interface

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Frequently Asked Questions (FAQs)

Q1. What does it mean for a class in OOP to be abstract?

A class with one or more abstract methods is said to have an abstract class. An abstract class is a template description of the methods and variables of a type (a category of objects).

The object-oriented programming (OOP) languages Java (see Java abstract class), C++, C#, and VB.NET use abstract courses in their respective programming frameworks.

Q2. What sorts of classes are said to be abstract?

In object-oriented programming, an abstract class could feature abstract methods or characteristics shared by the subclasses it contains. Abstract courses are allowed to have subclasses in certain circumstances.

Various names, including traits, mixins, flavors, roles, and type classes, refer to language characteristics. Abstract types may be constructed using any of these features (or that have the potential to be utilized).

Q3. How may an abstract class be distinguished from other types of classes?

An abstract class cannot be instantiated in any way, shape, or form. Including abstract versions of methods and accessors in an abstract class is permissible.

Applying the sealed modifier to an abstract class is not feasible because the two modifications have diametrically opposite implications.

Q4. What are the primary functions of an interface?

In Java, abstraction is accomplished via the usage of interfaces. Java classes can implement an interface by making use of the implements keyword.

An interface may be seen as a container that retains the signatures of the methods that will be implemented in the code segment. This definition of an interface is somewhat general. The degree of abstraction is increased.

Q5. The use of interfaces in Java has several advantages; what are they?

Java provides a means for achieving abstraction in the form of an interface. Only abstract methods are allowed in the Java interface, but method bodies are never allowed.

Abstraction and multiple inheritances may be accomplished using Java with the help of this tool. Put another way. You might argue that interfaces can include abstract methods and variables.

Differences Between Abstract Class And 

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