Top 16 Java Architect Interview Questions & Answers

A Java architect manages all the systems and applications that run Java applications. Doing that requires a thorough understanding of the Java programming languages along with all of its nuances. 

Since Java is supposedly one of the most difficult programming languages to master, you might feel stuck while preparing for Java interviews due to its functions’ sheer verbosity and complexity. At upGrad, we understand your struggles and are here to help you through them. 

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Key Topics for Java-related jobs

There are some key topics that you must not skip past while preparing for any Java-related jobs or interviews in all its vastness. Some such issues include: 

• Java Programming Overview.
• Details about Java and the paradigm it operates on (OOPS).
• JDK, JRE, JIT, JVM – Java compilers.
• Variables and Operators in Java.
• Loops and methods. 
• Data structures – including Arrays, Lists, Heaps, Trees, etc. 
• Classes and Objects
• Important keywords – like ‘this,’ ‘super,’ and more. 
• Abstract Classes and Interfaces.
• Servlets in Java.
• Multithreading in Java.
• Advanced concepts in Java. 

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It’s not possible to ask questions from all the topics in this blog. So, it is recommended that you most definitely explore the above-mentioned topics and get more insights on them.

Java Architect Interview Questions & Answers

Here we are list the top 17 Java interview Architect interview questions based on most of the themes mentioned above. Please remember that this is NOT a comprehensive list of questions – it is to give a flavor of what you can expect. You will have to do some more digging since Java demands time! 

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1. What are access specifiers, and what kinds of access specifiers are available in Java?

Access specifiers can be thought of as keywords used before defining or naming any class to establish the access scope of that class. Java supports the following access specifiers for classes, methods, and objects:  

• Public
• Protected
• Default
• Private

2. How do an inner class and a subclass differ in Java? 

Inner classes are those that are nested inside another class. Therefore, inner classes have access rights for all the variables and methods of the outer type. 

On the other hand, a subclass is a special type of class that inherits its features from another class known as a superclass. A subclass can access all protected and public methods and fields of the superclass. 

3. What is the significance of data encapsulation? 

Data encapsulation is one of the primary concepts of the OOP (Object Oriented Programming) paradigm and is used to combine different methods and properties into a single unit. Using encapsulation, programmers can follow a structured, modular approach for software development. Encapsulation is also useful for data hiding purposes. 

4. What are singleton classes in Java? 

Singleton classes are those that can have only a single instance. That is why all of the variables and methods will belong to just one instance. The concept of singleton classes is extremely useful for situations wherein the programmer needs to limit the number of objects available in a class. 

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5. How do double, and float variables differ in Java? 

In Java, double takes 8 bytes in memory while float takes 4 bytes. Moreover, double is a double-precision floating-point number, while float is single precision. 

6. What is the Final Keyword in Java? 

In Java, if a programmer wishes to declare a constant, they use the Final keyword. Any element defined with a Final keyword cannot have its values changed at a later stage. When a method is final, it cannot be overridden by its subclasses. Also, the Final methods are faster than the remaining since they are resolved at compile time. 

7. What are the ways to generate random numbers in Java?

Java provides two ways for programmers to generate a random number: 

• Using Random class in the package java.util
• Using Math. random() would generate random numbers in the range from 0.1 to 1.0. 

8. Is it possible for the main() method in Java to return any value? 

No, Java’s main() method is always declared with a Void data type and can therefore not return any value. 

9. How does an Abstract Class differ from an Interface in Java? 

The key difference between Interface and Abstract Class is that the former only allows the declaration of public static methods. It does not hold any implementation of the said methods. Abstract Classes, on the other hand, can have any access specifiers with or without any implementation within classes. Another difference is that a class that implements an interface is required to implement all the methods of the interface. With Abstract Class, on the other hand, this is not a requirement. 

10. In Java, does importing packages automatically import sub-packages? 

No. If we import packages, only the packages will be imported, and not the sub-packages. The programmer needs to import the sub-packages separately if required. 

11. How do equals() and == differ in Java? 

The equals() method is defined in Object Class for checking the equality of two objects. This method can be overridden if needed by the programmer. The equality operator (==), on the other hand, is a binary operator which returns only boolean values. 

12. What is the difference between a local variable and an instance variable?

A local variable is used within a constructor, a method, or a block – and it is local to that particular scope. Other methods or blocks in the class won’t be aware of a variable that is not local to their scope. 

Instance variable, on the other hand, is bound to its object. These variables find their declaration within a class but outside the method. That way, all the methods or blocks of that class have access to the instance variable. 

13. What are collections in Java? 

Collection, in Java, is a framework that can be thought of as a skeleton or architecture for saving and manipulating different groups of objects. Collections allow programmers to perform various important tasks like sorting, searching, manipulation, insertion, deletion, etc. The collection framework in Java includes the following: 

• Interfaces
• Classes
• Methods

14. What are the different methods in Servlets for session management? 

Sessions are communicational states between the server and the client. As a result, one session can consist of multiple responses and requests. Since the Web Server and HTTP are both stateless, a session is maintained only when session ID (or some unique identifier about the session) is passed between client and server in all the requests and responses. Some of the methods for server management include: 

• HTML hidden fields
• Cookies
• URL Rewriting
• User authentication
• Session management API

15. What are JDBC statements?

JDBC statements can be understood as the statements that are required to communicate with the databases using SQL commands. JDBC provides various methods like executeUpdate(), execute(), and executeQuery() to interact with the database. 

JDBC three offers the following three types of statements: 

• Statement: Think of this as the general purpose of executing SQL queries at runtime and accessing the database. 
• PreparedStatement: This is used when the programmer wishes to provide input parameters and the SQL queries during execution. 
• CallableStatement: This is used to access the stored procedures. CallableStatement accepts runtime parameters.

16. How is exception handling done in the Spring MVC Framework? 

Spring MVC provides the following ways to set up exception handling in our program: 

• Controller-based: In this, we define exception handler methods. All we need to do is prefix these methods with @ExceptionHandler annotation. 
• Global exception handler: @ControllerAdvice annotation is used for this. Any class can be used to define the global exception handler. 
• HandlerExceptionResolver implementation: Spring MVC provides HandlerExceptionResolver to create global exception handlers. This method is because the Spring framework also offers some default classes that can be defined in our spring bean configuration file to get exception handling benefits.

17. What is the difference between the Java Virtual Machine (JVM) and the Java Development Kit (JDK)?

The JVM and JDK are essential components of the Java platform. They serve different purposes. The JVM is a virtual machine that enables Java bytecode to be executed on any platform, providing platform independence. On the other hand, the JDK is a software development kit that includes the necessary tools and libraries to develop, compile, and debug Java applications.

18. Explain the concept of method overloading in Java.

Method overloading is a feature in Java that allows multiple methods with the same name but different parameters to coexist within a class. It enables developers to perform similar operations on different data types or numbers of arguments. During compilation, Java determines which method to invoke based on the method’s name and the number and types of its parameters.

19. What is the role of the “throws” keyword in Java?

The “throws” keyword is used in Java to declare that a method may throw a specific type of exception during its execution. It is in the method signature after the parameter list and before the method body. By using “throws,” the method indicates that it is not handling the exception internally and will propagate it to the calling code or the invoking method.

20. How is method overriding achieved in Java?

Method overriding is an aspect of inheritance in Java. It occurs when a subclass provides a specific implementation for a method already defined in its superclass. To achieve method overriding, the method in the subclass must have the same name, return type, and parameters as the method in the superclass. By doing so, the subclass can override the behavior of the superclass method.

21. What are Lambda expressions in Java, and how do they simplify coding?

Lambda expressions, introduced in Java 8, are anonymous functions that can implement functional interfaces. They enable developers to write concise and more readable code by reducing the verbosity associated with traditional anonymous inner classes. Lambda expressions can be handy when working with functional interfaces, such as those used in streams and functional programming.

22. What is the difference between the “==” operator and the “equals()” method when comparing objects in Java?

In Java, the “==” operator compares primitive data types for equality, while the “equals()” method is used to compare objects for content equality. The “==” operator checks if two objects refer to the memory location, whereas the “equals()” method checks if the content or state of two objects is the same. It is essential to override the “equals()” method in custom classes for meaningful content comparison.

In Conclusion

As mentioned earlier, the questions listed above are in no way sufficient to help you crack the interview. They are just the top few questions that are mostly asked across different Java Architect interviews. However, they will give you a good understanding of the kind of expertise the interviewers are looking for. So, without further ado, get started with your preparations and ace the next interview! 

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