Most Common Java Design Patterns Interview Questions and Answers 2020

Design patterns are usually sets of standardized practices within the software development industry. Java Design Patterns represent the solutions distributed by the location to general problems faced in every-day tasks regarding software development.

Let’s have a look at the most regularly asked design pattern interview questions and answers. These questions can help you together with your coding interviews and also competitive exams.

Here is the set of Most Common Java Design Patterns Interview Questions and Answers

Both OOP and GOF design pattern interview questions certainly are a fundamental element of any good set of core Java interview questions. Java is among the most popular Object oriented programming language on the globe and has plenty of design pattern and design principles, contributed by many developers and open source framework and being truly a Java programmer since 24 months its expected from you to learn concepts like OOPS concepts Abstraction, Encapsulation, and Polymorphism, What’s design pattern in Java, Some popular Java design pattern and most importante when or where you can use those design pattern in Java application. The purpose of asking design pattern interview question in Java is to be sure of whether Java programmer knows those essential design patterns or not.

We should understand that in Java interviews Design patterns are very important like multi-threading, collection, and programming questions. If you are senior or experienced Java programmer than expecting more technical and tough design pattern in Java interview e.g. Design pattern like Chain of Responsibility and solving in real-time the program design questions is a wonderful thing.

#1. How is Bridge pattern differs from the Adapter pattern?

The motive of the Adapter pattern is to create interfaces of one or more classes to look similar.

The Bridge pattern is designed to isolate a class’s interface from its implementation so we are able to vary or substitute the implementation without changing your client code.

#2. When to use Strategy Design Pattern in Java?

Java design pattern interview question and answers for senior and experience programmerStrategy pattern in quite ideal for implementing set of related algorithms e.g. compression algorithms, filtering strategies etc. Strategy design pattern gives you to build Context classes, which uses Strategy implementation classes for applying business rules. These pattern follows open closed design automatically principle and quite useful in Java.

JDK states that Among most well-known Strategy pattern itself is a Comparator interface and Collections.sort() which is a great strategy interface and defines a technique for like comparing objects. Due to this pattern, we don’t need to modify sort() method (closed for modification) to compare any object, at exactly the same time we are able to implement Comparator interface to mainly define completely new comparing strategy like in open for extension software.

#3. Briefly Explain Data Access Object (DAO) pattern?

Data Access Object Pattern is employed to isolate low-level data accessing API or actions from high-level business services. Following will be the elements in the DAO Pattern.

Data Access Object Interface

DAO interface describes the typical actions to be performed on a model object(s).

Data Access Object concrete class

This class implements a DAO interface. This class is accountable to get data from a databases which is often Xml/database or any other storage mechanism.

Model Object or Value Object

This object is an ordinary old java object containing get/set methods to store data retrieved using DAO class.

#4. What are the key Difference between State design and Strategy Pattern in Java?

That is a fascinating Java design pattern interview questions as both Strategy and State pattern gets the same structure. If you have a look at UML class diagram for both patterns they look accurately same, but their intent is very different.

State design pattern is employed to define and manage the state of an object, while Strategy pattern is employed to define a couple of an interchangeable algorithm and let’s client choose among these. So, guys, these main Strategy pattern is a customer driven pattern while Object will surely manage their state in every condition.

#5. What do you mean by MVC patterns?

This pattern is probably the most-used patterns from J2EE Design pattern category. It is quite similar to the idea of Model-View-Controller. The abbreviation MVC is extracted from the Model-view-controller concept.

Models are objects, used as blueprints for all of the objects that will be used in the application.

Views contain the presentational aspect of the info and information found in the models.

Controllers control both model and view because they serve as a connection between the two objects. The controller plays the role of an interface between View and Model and also intercepts all of the incoming requests.


We don’t think, you will face any confusion while reading this article, but if you feel something is wrong in this article, let us know in the comment section and we will reach at you immediately with its solution.

Leave a Reply

Your email address will not be published. Required fields are marked *