Advanced Java Interview Questions For Tech Lead

How does Garbage Collection prevent a Java application from going out of memory?

This is a tricky Java interview question… it doesn’t!

Garbage Collection simply cleans up unused memory when an object goes out of scope and is no longer needed. However, an application could create a huge number of large objects that causes an OutOfMemoryError.

What is the difference between final, finalize and finally?

final is a Java keyword used to indicate that either a method can not override in a subclass, or a class can not be extended or a field can not be modified. finalize is a method that gets called on an instance of an Object when it is garbage collected. finally is a Java keyword used in exception handling to indicate a block of code that should always be run whether an exception is thrown or not.

When do you use volatile variables?

When a member variable is accessed by multiple threads and want the value of a volatile field to be visible to all readers (other threads in particular) after a write operation completes on it.

1 What is the inferred type of the method reference System.out::println?

In this code:

what is the inferred type of the method reference System.out::println?

IntStream.range(0, 10) returns an IntStream, and IntStream defines a .forEach() method accepting an IntConsumer as an argument, whose prototype is:

System.out is a PrintStream, and a PrintStream has a method named println which takes an int as an argument and returns void. This matches the signature of an IntConsumer, hence the result.

What’s the difference between String, StringBuffer, and StringBuilder?

String is an immutable class. In older JDKs the recommendation when programmatically building a String was to use StringBuffer since this was optimized to concatenate multiple Strings together.

However, the methods StringBuffer were marked as synchronized, which meant that there was a performance penalty, hence StringBuilder was introduced to provide a non-synchronized way to efficiently concatenate and modify Strings.

1 Identify the problem in the below Java code:

A classic example of escaping references.

When an object of Bar is created, the super constructor in Foo gets called first, which in turn calls the ‘overridden’ doSomething method.

The doSomething method passes the this instance to the class Zoom. Zoom now can use the ‘this‘ instance before it is created entirely. BAD!!!

1 What is the problem with this code?

The problem is that the Stream returned by Files.lines() is not closed.

This should be used instead:

Stream extends BaseStream, and BaseStream extends AutoCloseable. While this has no influence on streams you obtain from collections for instance, the stream returned by Files.lines() is I/O bound. Neglecting to close it correctly may lead to a resource leak in the event of an error occurring while processing the stream.

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Java is an Object-Oriented programming language used by the vast majority of programmers worldwide. Technical interviews at top companies frequently include advanced Java interview questions based on coding and programming theory. If you are preparing for a Java developer or software engineering interview, these advanced Java interview questions will help you understand the types of questions that will be asked.

If you’re a software engineer, coding engineer, software developer, engineering manager, or tech lead preparing for tech interviews, check out our technical interview checklist, interview questions page, and salary negotiation e-book to get interview-ready!Â

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Let’s look at some advanced Java interview questions for freshers and experienced developers that feature in FAANG+ interviews.

Here’s what we’ll discuss:

  • Top Advanced Java Interview Questions and Answers
  • Advanced Java Interview Questions on Multithreading
  • Advanced Java Interview Questions on OOPs Concepts
  • FAQs on Advanced Java Interview Questions
  • Live Interview | Accenture | Technical Lead | Java | Spring Boot | Web Services | Microservices

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