Updated June 17, 2023
Introduction to Java Developer Interview Questions And Answer
Java, the mother of modern-day tools and complex languages, is the preferred choice of application developers, data scientists, and machine learning enthusiasts. This is why having Java skill sets is a boon, as there are a host of companies hiring for the skill set. Are you heading off to a Java developer interview anytime soon and biting your nails as to what, in most probability, you would be quizzed on? Then this is the article for you to swear by.
So if you have finally found your dream job as a Java Developer but are wondering how to crack the 2023 Java Developer Interview and what could be the probable Java Developer Interview Questions, every interview is different, and the scope of a job is different too. Keeping this in mind, we have designed the most common Java Developer Interview Questions and answers to help you get success in your interview.
Below are the 10 important 2023 Java Developer Interview Questions and Answers that are frequently asked in an interview. These questions are divided into parts are as follows:
Part 1 –Java Developer Interview Questions (Basic)
This first part covers basic Interview Questions and Answers
1. What is the difference between JVM, JDK, and JRE?
Answer:
JVM: JVM stands for ‘Java Virtual Machine’ is an abstraction for a machine in Java. This is the necessary abstraction environment necessary for the Java bytecode to be executed in. A runtime instance of the virtual machine is incepted whenever the java command is executed on the command prompt.
JRE or ‘JAVA Run-time Environment’ is the very environment, which implements the JVM by providing class files and libraries it uses to run the bytecode at runtime. In essence, this is a software instance of the JVM, which, unlike the JVM, has a physical existence.
JDK is the superset here, which engulfs and contains JRE and is really a framework where compilation and documentation of Java programs are performed into packages.
2. Explain the ‘Platform independence ‘properties of java.
Answer:
The very essence of the platform independence of Java lies in the way the code is stored, parsed and compiled – bytecode. Since these bytecodes run on any system irrespective of the underlying operating system, Java truly is a platform-independent programming language.
3. Differentiate between heap and stack memory in Java on the grounds of the use of the memory, the basic features, and the validity.
Answer:
| DIFFERENTIATING PARAMETER | STACK MEMORY | HEAP |
| Memory uses | A single thread in the execution employs the stack memory. In this way, the objects stored in the stack memory cannot be accessed by all the other threads. | Heap memory is used by various modules and components of the application. All the threads and other constructs can access the various objects which are stored in a heap. |
| Lifetime and validity of the use | Stack memory, which is dedicated to a particular thread, is only actively useable until the time that the thread lasts. | The heap can be used globally, and hence its useable active lifetime is the entire time during the program execution. |
| Overall use | Whenever an object is created for a particular thread, the local primitive and reference variables are associated with the object. These very variables are stored in the stack memory. | Any object that gets created during the overall program execution is stored within the heap. This may not be limited to a single thread, but all the concurrent or subsequent threads being created and called for. |
4. Explain the meaning and the use of the static keyword in java.
Answer:
These are the basic Java Developer Interview Questions asked in an interview. Static is a commonly used keyword, which is associated with variables, methods, and nested classes in java. The real use of the keyword is for memory management of these constructs, as detailed next.
1. Static variables in java: When a variable is created as static in Java, it gets memory allocated to it only once, and that too when the class in which it is declared gets loaded. This is why these variables are used to declare properties of other variables shared amongst them and do not change.
2. Static methods in java: Methods in java can also be declared as static, and as such, these are then connected to the entire class without being limited to any single object of the class. Invocation of such a method declared as static does not require the instance of the class, and these methods can work on the static data of the class and can even make updates to the value of static constants and variables.
This is also why the main function in java is by default static, and hence no object is required to invoke it, which leads to better memory management.
Part 2 –Java Developer Interview Questions (Advanced)
Let us now have a look at the advanced Interview Questions.
5. Explain the use of the ‘this’ keyword in java
Answer:
The ‘this’ keyword is widely observed in all java codes and scripts, and it, in fact, is a reference variable that programmers use to refer to the current object in use. The method of the current class can be suitable invoked using the ‘this’ keyword. The java compiler implicitly adds the keyword to the method if you do not specify the same.
6. Explain what pointers are and elaborate if they can be used in java?
Answer:
Pointers are a special class of variables that are available in a lot of programming constructs such as C++. These are used to reference a particular position in the memory, and this is coming off as a very powerful way of explicit memory allocation, management, and traversing amounts of memory units.
Pointers are, however, not supported or available within Java, as they can get quite complex with the segregation of the stack and the heap memory in java.
Let us move to the next Java Developer Interview Questions.
7. Explain the concept of object cloning and how is this used in java?
Answer:
These are the advanced Java Developer Interview Questions asked in an interview. There are times when one needs to use the exact copy of an object for a specific purpose without changing the actual object in any way. The option, in this case, is to create another similar object, which will require a greater amount of memory to be expensed, and this is where the construct of object cloning provided by java comes to prove beneficial.
The clone() methods of the object class implement object cloning and require the implementation of the java.lang.A cloneable interface of the object class whose clone you are trying to create. Devoid of this, a CloneNotSupportedException is generated by the clone() method of the class.
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