While an older language, Java remains one of the most popular high-level programming languages today. It entered the landscape as a high-level language designed for simplicity and platform independence. Java is running on most of our mobile devices and laptops, and Java developers remain in high demand.
Whether you’re preparing for a role in game development or Android development, mastering Java might take you closer to finding a developer job you love.
Today, we present you with this complete guide to preparing for Java interviews.
We’ll cover:
Java can be considered a partially object-oriented programming language. Java supports object-oriented programming along with other programming paradigms. Java employs object-oriented programming (OOP) concepts including encapsulation, polymorphism, inheritance, and abstraction.
However, Java is not a pure object-oriented programming language. It fails to satisfy the pure OOP language requirement that all user-defined types are objects. Java supports primitive data types as well
No, Java doesn’t support multiple inheritances for classes. Java was designed for simplicity and multiple inheritances for classes was avoided to avoid the “Deadly Diamond Problem.” This problem results when a child class has two parent classes with two different methods for implementing a feature.
JDK stands for Java Development Kit. JDK consists of the Java Virtual Machine (JVM) and Java Runtime Environment (JRE), which are essential to Java development.
Given two overloaded methods, which method will be invoked for the method call myOverloadedMethod(5)
?
void myOverloadedMethod(long arg) { System.out.println("Method with long invoked"); } void myOverloadedMethod(int arg) { System.out.println("Method with int invoked"); }
Choose an answer.
Which method will be invoked for the method call `myOverloadedMethod(5)?
method with int
method with long
Execute the following code to verify the result.
class Demonstration { public static void main( String args[] ) { myOverloadedMethod(5); } static void myOverloadedMethod(long arg) { System.out.println("Method with long invoked"); } static void myOverloadedMethod(int arg) { System.out.println("Method with int invoked"); } }
If no constructors are defined for a class, the compiler generates a nullary constructor known as the default constructor.
To prepare for basic Java interviews, check out these resources:
Enum is a special data type or class that’s used to store constants. Since enum is a type, it can implement an interface.
The JVM references GC roots to guide the garbage collector. GC roots allow the garbage collector to collect only those objects that need collection.
Java has four types of GC roots:
Garbage collection in Java occurs in three phases: Marking, deletion, and promotion.
REST APIs are very popular in Java development.
Some questions you may be asked to assess your depth of knowledge on REST include:
Be sure to spend plenty of time studying REST API interview questions and answers.
To prepare for advanced Java interviews, check out these resources:
Coding interviews will test your familiarity with Java, your understanding of algorithms and data structures, and your problem-solving skills. The higher the level of the role, the more likely this test will touch on topics such as system design, bit manipulation, and concurrency.
Here are some resources to get you started preparing for a Java coding interview:
As with any coding interview, you’ll want to study several algorithms and be prepared to implement them in Java.
Some algorithms to study include:
You can learn about these common Java algorithm questions and more by taking our course, Algorithms for Coding Interviews in Java
You’ll want to know the fundamentals of data structures in Java. You should know how to declare and initialize data structures, and practice performing different operations on them. It’s a good idea to spend time studying common Java data structure interview questions questions and answers.
Some topics you should be sure to study are:
Collections are objects grouping multiple elements into a single unit. The Java collections framework identifies classes and interfaces with which we can implement collections.
The collection interface is used to pass around collections of objects.
The core collection interfaces are:
Bulk operations are operations that can be performed on an entire Collection. Bulk operations include containsAll
, addAll
,removeAll
and more.
There are three collection types in the Java collections framework: Ordered lists, maps, and sets.
Other Java collections interview questions could consist of:
Learn how to answer these questions and more through our course on Collections in Java. You’ll learn how to sort collections, modify data in collections, and how to make collections thread-safe.
Multithreading is increasingly important for senior level roles. Multithreading is a resource-efficient way to multitask in Java.
Multithreading is a technique that allows us to efficiently leverage CPU by executing two or more threads concurrently.
Benefits of multithreading include:
Other questions on multithreading might concern:
Learn how to answer these questions and more by studying Java multithreading interview questions for senior engineers.
Java 8 introduced several valuable new features, including the Lambda expression, virtual extension methods, a new Date and Time API, as well as support for functional programming.
Check out our course for a deep dive on mastering the features in Java 8
Function composition is one of the 5 key principles of functional programming. It refers to combining simple functions to create a complex function.
Functional interfaces are interfaces that have a single abstract method. Functional interfaces are implemented with Lambda expressions. The Lambda expression contains the body of the abstract method.
Stream API questions questions can include:
Check out our blog post on mastering Stream API for answers to these questions and more.
Other questions on Java 8 could include:
random
keyword used for?You can find answers to these questions and more in this article covering the top Java 8 interview questions.
If you’ll be working with the Java Enterprise Edition, or Jakarta EE, you’ll likely be asked about web frameworks such as Spring and Hibernate.
Spring framework questions can include the following:
You can find answers to these among the top 40 Spring framework interview questions.
Hibernate’s core interfaces are:
Singleton beans are not thread-safe. A singleton is a design pattern for creation. Thread safety is specific toward execution.
How much you prepare depends on your experience. If you’re interviewing for a job with additional language requirements, you won’t be able to spend all of your time on Java. You’ll want to use your time wisely and cover as many bases as you can during interview prep.
If you’ve been working with Java for a while, you can skip this.
Before you start preparing for interviews, make sure you’re well-versed on the fundamentals of Java programming.
Check out our learning path tailored for Java for programmers .
You’ll often go through several rounds of interviews, from behavioral interviews to coding interviews, up to system design interviews.
You’ll want to practice answering various interview questions. Since you have limited time to prepare, it’s important to have a strategic coding interview prep plan. In addition, you need to plan for what to do if you’re given a coding problem you can’t solve (Hint: You can still get the job).
Here are some resources to help you prepare:
How much time will you need?
Check out this coding interview roadmap.
The system design interview is common practice if you’re interviewing for a role as a senior developer.
Here are some resources to help you prepare for the Java system design interview:
All interviews vary! In addition to studying industry-standard interview questions, you should tailor your interview preparation for your unique circumstances:
Here are some additional resources that are specific to company interviews:
There are several ways to approach preparing for a Java interview. You’ll want to review fundamental concepts based on your experience level. You’ll also want to get hands-on practice with real-world problems. You’ll want to tailor your preparation based on the level and responsibilities of the job you’re applying for, as well as the company. While you can’t know everything about an interview in advance, there’s a lot you can do to be sure you walk in prepared.
At Educative, we love to support developers as they advance in their careers. That’s why we created Interview Prep with Educative. Here, you’ll find all our resources for Java interview prep in one place, from courses and tutorials to walkthroughs on real-world interview problems.
We’ve also created these courses and learning paths to help you master Java programming and and ace your Java interview:
These courses are not specifically designed for interviews, but they’re interactive and cover other essential skills for Java interviews:
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