Top 50 Java Design-Pattern Interview Questions

Introduction: Design Pattern Interview QuestionsUpdated 2020 edition This book contains the Design Pattern Technical interview questions that you can expect in a Java interview. Design Pattern is a very important topic in technical interview. Many fortune 500 organizations use Design Patterns. This book contains basic to expert level Design Pattern interview questions that an interviewer asks. Each question is accompanied with an answer so that you can prepare for job interview in short time. Often, these questions and concepts are used in our daily programming work. But these are most helpful when an Interviewer is trying to test your deep knowledge of Design Pattern concepts.How will this book help me?By reading this book, you do not have to spend time searching the Internet for Design Pattern interview questions. We have already compiled the list of the most popular and the latest Design Pattern Interview questions.
Are there answers in this book?Yes, in this book each question is followed by an answer. So you can save time in interview preparation.
What is the best way of reading this book?You have to first do a slow reading of all the questions in this book. Once you go through them in the first pass, mark the questions that you could not answer by yourself. Then, in second pass go through only the difficult questions. After going through this book 2-3 times, you will be well prepared to face a technical interview for Software Engineer position in Design Patterns programming.
What is the level of questions in this book?This book contains questions that are good for a Associate Software engineer to a Principal Software engineer. The difficulty level of question varies in the book from a Fresher to an Experienced professional.
What are the sample questions in this book?

• When will you use Strategy Design Pattern in Design Pattern?
• What is Observer design pattern?
• What are the examples of Observer design pattern in JDK?
• How Strategy design pattern is different from State design pattern in Design Pattern?
• Can you explain Decorator design pattern with an example in Design Pattern?
• What is a good scenario for using Composite design Pattern in Design Pattern?
• Have you used Singleton design pattern in your Design Pattern project?
• What are the main uses of Singleton design pattern in Design Pattern project?
• Why Design Pattern.lang.Runtime is a Singleton in Design Pattern?
• What is the way to implement a thread-safe Singleton design pattern in Design Pattern?
• What are the examples of Singleton design pattern in JDK?
• What are the examples of Visitor design pattern in JDK?
• How Decorator design pattern is different from Proxy pattern?
• What are the different scenarios to use Setter and Constructor based injection in Dependency Injection (DI) design pattern?
• What are the different scenarios for using Proxy design pattern?
• What is the main difference between Adapter and Proxy design pattern?
• What are the examples of Adapter design pattern in JDK?
• What is the difference between Factory and Abstract Factory design pattern?
• What is Open/closed design principle in Software engineering?
• What is SOLID design principle?
• What is a Data Access Object (DAO) design pattern?