Java Mock Interview | Interview Questions for Senior Java Developers

Summary

In this interview, Jose, a tech leader from Turing, interviews James, an experienced Java developer, discussing his professional background, key projects, and technical expertise. James shares his journey from working on a Coca-Cola Africa project to developing Java applications in various industries, with insights into constructor overloading, exception handling, garbage collection, and RMI architecture. The conversation also delves into topics like applet life cycles, DGC (Distributed Garbage Collection), and string length functions in Java. This informative session offers a deep dive into Java development with real-world examples and insights from a seasoned developer.

Takeaways

• 😀 The interview is with James, a seasoned software engineer, with a background in Java and mobile development, particularly iOS.
• 😀 James shares that his first significant project was for Coca-Cola Africa, developing an environmental data tracking system using Struts, JSPs, and Servlets.
• 😀 He also worked on a Java application for quality assurance in bottling plants, which monitored bottle pressure and checked for contamination in liquids.
• 😀 The conversation covers Java-related topics, including constructor overloading, which allows different constructors in a class with unique parameters to customize object creation.
• 😀 James explains how constructor overloading and copying work in Java, highlighting that classes are passed by reference and that careful handling is needed when copying objects to avoid unintended behavior.
• 😀 When discussing exceptions in Java, James distinguishes between checked and unchecked exceptions, emphasizing that checked exceptions must be handled during compilation while unchecked exceptions are typically caused by logical errors during runtime.
• 😀 The difference between the 'final' block and the 'finalize' method in Java is explained, where the final block ensures code execution upon exiting a try block, and the finalize method is for cleaning up resources before an object is garbage collected.
• 😀 James explains that garbage collection in Java occurs in the permanent generation (permgen) space, and if this space is full, a full garbage collection may be triggered.
• 😀 Applet lifecycle in Java is covered, detailing the five stages: init, start, paint, stop, and destroy, each serving a specific function in the execution flow of applets.
• 😀 The difference between loading an applet over the internet versus from the file system is explained. Applets from the file system have more access to the user's computer, such as reading and writing files, whereas applets from the internet are subject to security restrictions.

Q & A

What is the primary role of the interviewer, Jose, at Turing?

Jose is a tech leader at Turing, responsible for hiring the best engineers by assisting with the vetting process. He has more than 17 years of experience, with expertise in JavaScript.

Can you describe the types of projects James has worked on throughout his career?

James has worked on various projects, including an environmental data tracking website for Coca-Cola Africa and a Java application used in bottling plants to monitor the quality of bottles and cans.

What is constructor overloading in Java, and how does it work?

Constructor overloading in Java allows a class to have multiple constructors with different parameters. It helps create instances of a class in different ways depending on the data available, making object construction more customizable.

What is the difference between checked and unchecked exceptions in Java?

Checked exceptions are those that are checked at compile time, and the code must handle them using a try-catch block. Unchecked exceptions, such as runtime exceptions, are not checked at compile time and typically occur due to logical errors in the code.

What is the difference between the 'final' block and the 'finalize' method in Java?

'final' is used in a try block and ensures certain cleanup actions (like deleting temporary files) are performed regardless of whether an exception occurs. The 'finalize' method, which is part of the Object class, is used by the garbage collector to clean up resources before an object is deleted.

Can a developer override the 'finalize' method in Java?

Yes, a developer can override the 'finalize' method in Java, but it is generally not common practice. It is meant for cleanup actions before garbage collection, and overriding it requires careful management of resources.

How does garbage collection occur in the Permanent Generation (PermGen) space of the JVM?

Garbage collection in PermGen space occurs when this space becomes full or crosses a certain threshold, triggering a full garbage collection cycle. Proper sizing of PermGen space is essential to avoid frequent full garbage collections.

What are the five stages in the life cycle of an applet in Java?

The five stages in an applet's life cycle are: init (initialization), start (starts execution when a browser is maximized), paint (displays content), stop (when the browser is minimized), and destroy (when the applet is closed).

What is the difference between an applet loaded over the internet and one loaded from the local file system?

An applet loaded over the internet is subject to security restrictions imposed by the applet security manager, while an applet loaded from the local file system has more access to the user's computer, allowing file reading, writing, and process execution.

What is Distributed Garbage Collection (DGC) in RMI, and how does it work?

Distributed Garbage Collection (DGC) is used in Remote Method Invocation (RMI) to manage memory for remote objects. It ensures that objects referenced across different machines or JVMs are not prematurely deallocated. DGC uses a reference-counting algorithm to manage remote object references.