Giving an interview can be a nerve-wracking experience for anyone. Whether you are a fresher or an experienced professional, being prepared for an interview is necessary. If you are a programmer, being proficient at Java is a must. Along with having a sound working knowledge, you also need to have technical knowledge of Java. Questions regarding Java and other programming languages are very common in interviews. Therefore, here is a list of the most commonly asked Java interview questions. Remember, preparing answers to these questions will ensure that your interview goes smoothly.
Types of Java Interview Questions
If you are someone who works with Java, you must be aware that it is quite comprehensive. Therefore, it is necessary that you are aware of all the keywords, new technologies, and details of Java. In the case of interviews, there are specific categories in Java that interviewers cover. Experts list down the types of Java interview questions that candidates should expect. Some of the important categories of questions include basic interview questions, OOPs interview questions, spring handling questions, etc. Now, let us discuss each of these Java interview questions in detail.
Basics of Java
It is obvious that interviewers will start by asking the basic questions. Thereafter, they will move on to the advanced ones. Here, it is important to remember the core concepts and definitions of Java. Even if you have a good working experience with Java, you need to be confident about your theoretical knowledge. It is essential to know about the origin, development, and history of Java. Therefore, it is a good idea to remember the key logistics relating to the program. For example, you should have clear answers regarding the meaning of Java, its release date, and its creator.
Next, the interviewers will focus on asking the defining concepts and features of Java. Thus, they will ask questions regarding the features of Java, the differences between Java and other programming languages, etc. Further, they may include questions relating to platforms, JVM, JDK, and JRE. Even though these are basic questions, it is important that you answer them in a correct manner. Remember, your answers should be precise, clear, and to the point. Your interviewers will ask you follow-up questions on the basis of your initial answers. Therefore, it is essential that you create a good first impression.
Let us consider some of the basic Java Interview Questions. Firstly, the interviewer may ask you to define Java and mention some of its features. He may also ask to explain the difference between Java and C++. Additionally, the interviewer may ask questions relating to Java Virtual Machine. Further, they can ask about Java Development Kit. Some other basic questions relating to JIT compiler, Java platform, packages, etc. are common.
Once interviewers cover the basic question, they move ahead to ask specific questions. So, this means that they will pick a topic and ask conceptual questions that you must answer. Generally, the first category in this set of questions is the OOPs Java Interview Questions. OOPs stands for Object Oriented Programming. In this category itself, there are subtypes of questions that the interviewers ask. The interviewers will start by asking the meaning of Object Oriented Programming and the main concepts in it. Thereafter, they will move on to methodical questions.
Experts divide OOPs Java Interview Questions into specific categories so that it is convenient for the candidates to prepare. The sections of OOPs interview questions include topics relating to the constructor, static keyword, polymorphism, inheritance, abstraction, etc. Now, let us check out some common questions that interviewers ask for each section.
Basic OOPs Interview Questions
For the basic OOPs questions, they will ask to explain what Object Oriented Programming is. Secondly, they can ask about the object-oriented paradigm. Additionally, some interviewers may ask you the difference between object-oriented programming and object-based programming. Finally, they can ask you to define the object and some of its relevant concepts.
Constructor and Static Keyword Questions
The following are some of the most common Constructor Java Interview Questions: Questions regarding constructor and the types of constructor. Then, they will ask about the purpose of Default constructor and Parameterized constructor. They can also ask if a constructor in Java is inherited or not. Further, questions about constructor chaining and copy constructor are common. Interviewers may also ask about the overloading of the constructors.
The list of Static Java Interview Questions can include some of these questions – Questions about static variable and static method. At times, they may also ask about the static block. Interviewers can ask you to state the differences between the static method and the instance method. Finally, they can also ask if you can make constructors static. Sometimes, restrictions of the static method is also one of the questions.
Polymorphism and Inheritance Questions
Let us look at the list of some common Polymorphism Java Interview Questions. Firstly, interviewers ask the meaning of polymorphism. Next, they will ask the types of polymorphisms and their differences. Therefore, you should know the difference between runtime polymorphism and compile-time polymorphism. Additionally, they may ask you to explain static and dynamic binding.
The important Inheritance interview questions are given here. First, they will ask the definition of inheritance and the types of inheritance. Next, they will ask the meaning of things like aggregation and composition. They may also ask you to state the advantages of inheritance. Additionally, they generally ask questions about the “this” keyword. Sometimes, they also ask about the super keyword.
Read ahead to see some of the essential Abstraction interview questions. Firstly, they will ask about abstraction and abstract class. Next, they may ask you about interface. Additionally, they may ask the difference between abstract class and interface. Some other questions can be regarding read-only and write-only class. Also, there may be questions on interface like marker interface. They may also ask you to explain the difference between abstraction and encapsulation.
Method Overloading and Method Overriding
Some of the Method Overloading interview questions are questions like explaining the method overloading. Further, they may ask details about method overloading. These can include the main method, static in method overloading, and type promotion.
Some of the Method Overriding interview questions include the difference between method overloading and method overriding. Further, there are questions regarding whether you can override the static or private methods.
Final Keyword and Package
Here are the important Final Keyword Java Interview Questions: Explain the final variable and final method in Java. Secondly, explain the final class and final blank variable. Next, they may ask to explain the difference between the final method and the abstract method.
Now, here are some of the package interview questions: Explain package and give the advantages of defining packages. They may also ask you the process of creating a package in Java. In addition, they can ask if you can import the same package twice
The next set of questions will be regarding Exception Handling in Java. Now, this section is important as exception handling is an essential mechanism in Java. It maintains the flow of the program in Java. Therefore, you need to be thorough in your answers. Exception handling prevents errors in Java and thus, you should also prevent errors in answering these questions! Read on to see the common Exception Handling Java Interview Questions.
Interviewers may start by asking the types of exceptions and the concept of exception handling. Next, they may ask the difference between checked and unchecked exceptions. They may also ask you to explain the difference between throw and throws. Additionally, there may be questions regarding the hierarchy of exception classes and exception propagation. Interviewers also ask questions about the base class as well as the “finally” block
String handling is another crucial topic in Java. It involves the manipulation of data. Thus, it is yet another technical concept. In your interview, interviewers may ask you to demonstrate your practical skills. Thus, this section may involve theoretical questions as well as practical questions that you will have to solve. Generally, interviewers present a program and ask you to give the output of that program. Finally, the theoretical questions are given below:
Questions about String Pool are very common. There are questions about string literal and StringBuilder, and StringBuffer. Sometimes, interviewers may ask you to explain the different ways of creating the string object. Additionally, they may ask about the process of creating an immutable class.
Nested Classes and Interfaces
This next section of Java Interview Questions is easier than the rest. It includes very basic questions about classes and interfaces in Java. Thus, you can easily answer all the questions in this category if you are proficient in Java. Now, let us have a look at some of these questions.
There will be questions regarding the advantages and disadvantages of using inner classes. Interviewers will ask you to explain concepts of nested class and anonymous inner class. Next, there will be questions regarding the nested interface. Finally, they may ask about the relation between class and interface in Java.
Garbage collection involves the process of memory management in Java. There are chances that your interviewer may ask questions relating to garbage collection. Thus, here are some of the Java Interview Questions pertaining to garbage collection: Definition of garbage collection and what type of thread it is. Additionally, there may be questions regarding the purpose of the Runtime class and also the finalize() method. Sometimes, interviewers also ask the difference between final, finally, and finalize.
These topics are sufficient to go through when preparing for an interview for Java. However, if you want to go a step ahead, you can also consider brushing up on additional topics. Therefore, given below are some more topics that you can read up on before your Java interview.
I/O and Serialization
Here, there are questions about the hierarchy of InputStream and OutputStream classes. Another common question is to explain FileInputStream and FileOutputStream. They may also ask you about FilterStreams and Permissions. Sometimes, they ask the use of BufferedInputStream and BufferedOutputStream classes.
For serialization, they will ask you the meaning of serialization and deserialization. They will also ask about the transient keyword and externalizable interface. They may ask if you can transfer a serialized object via network. Finally, they may ask the difference between serializable and externalizable interface.
Networking and Reflection
In networking questions, interviewers may ask about Java socket programming. They may ask you to explain what a socket is. Generally, they also ask to describe the steps when two computers connect through TCP.
Reflection questions include explaining the process of reflection. Further, questions regarding class are common. There may also be questions about the purpose of using the javap command.
Miscellaneous Java Interview Questions
Finally, there may be miscellaneous questions like questions regarding wrapper classes and singleton classes. Questions relating to autoboxing and unboxing are also common. Object cloning, its advantages, and limitations is another common topic. Further, questions about peerless, lightweight, and heavyweight components are present. In some cases, there may be questions about the native method or the applet. You will also benefit from preparing topics like multithreading and concurrency in Java. You should prepare for theory as well as practical questions as they also ask many practical questions in interviews.
Thus, these are the different sections of Java questions that interviewers focus on. The list contains a comprehensive set of Java Interview Questions for freshers that interviewers usually ask. Preparing section-wise will ensure that you do not miss any component of Java. Remember, even if you have good working experience in Java, you should always prepare yourself for an interview. This list is a good resource to refer to when preparing for an interview. Additionally, you can also brush up on other concepts that are of special interest to you.