Most frequently asked Core Java Interview questions

It is one of the most requested languages in the IT industry. While there are several hardcore java developers, the language is quite complex to master. That’s why there is a great demand for Java developers who might not be so hard-core with their knowledge of the language but are experts in terms of practical usage. In this article, we will share with you some most important java interview questions so let’s get started.

Java Interview Questions for Fresher

So let’s get started with the first set of basic java interview questions and answers for freshers which is primarily useful for freshers. In fact, almost all those questions are asked in Java interviews even by experienced manager level programmers.

What is memory allocation in java?

There are five types of memory allocation in java:

• Class memory: In Java, when we only declare a variable of a class type, only a reference is created (memory is not allocated for the object). When it comes to primitive types, the entire data type is allocated when the variable declaration is made.
• Heap memory: In simplest terms, heap memory is a part of memory allocated to JVM, which is shared by all executing threads in the application. This type of memory is given to a Java application when it is initialized. It gives space for runtime classes.
• stack memory: A stack is a special area of a computer’s memory that stores temporary variables created by a function. In Stack, variables are declared, stored and initialized during runtime. Stack is also commonly known as LIFO (Last In First Out). They are called “last in first out” because the last variable that was added to the memory gets read first.
• Program Counter-Memory: It is necessary to know about program counter in programming. A program counter contains the memory location of the next instruction for the processor’s CPU to execute. It also helps in the execution of instructions as well as tracking the execution points. This will come in handy while coding and debugging purposes.
• Native method stack memory:  This memory is usually called native memory, native method stacks are not written in Java language. This memory is allocated for each thread when it’s created. And it can be of a fixed or dynamic nature.

Differences between Heap and Stack Memory in Java?

You can define a class by using the keyword class. To store the method implementation and local variables, stack memory is generally used. On the other hand, you can use heap memory to store objects. Before storing, they use dynamic memory allocation and deallocation. After explaining so much information, you will surely be able to explain this topic easily to others.

Define ClassLoader?

A class loader is a subsystem of the Java Virtual Machine (JVM) dedicated to loading classes. When a class is loaded from a Java application, an appropriate classloader will be used. The various features of all the classloaders available in JVM, the different types of classloaders and how they interact with the class, are not easy to understand at first glance.

Java Interview Questions for intermediate

What is JDK? And variants of JDK?

JDK (Java Development Kit) is an abbreviation for Java Development Kit. It is a combined Package of JRE and Developer tools used for designing java applications and Applets. Oracle has the following variants,

Variants of JDK

• JDK Standard Edition- The SE stands for Java Standard Edition is a computing platform in which we can execute software, and it can be used for the development and deployment of portable code for desktop and server environments.
• JDK Enterprise Edition- The Java Platform, Enterprise Edition (Java EE) is a collection of Java APIs owned by Oracle that software developers can use to write server-side applications. A developer can integrate (plugin) these APIs into their application to take advantage of the features Java EE offers.
• JDK Micro Edition- Java Platform, Micro Edition (Java ME) provides a robust and flexible environment for applications running on embedded and mobile devices in the Internet of Things. But with so much to choose from, it can be difficult to select the right technologies for your environment—for your next IoT project.

Difference between JDK, JRE, and JVM?

JVM: Java is an object-oriented programming language used for developing large applications. Java supports multiple platforms and has a Just in Time (JIT) compiler tool that converts all the Java source code into the low-level compatible machine language. Therefore, it runs faster than the regular application.

JRE: JRE has just essential classes library and runtime but doesn’t have any tool required for developing java applications.

JDK: Java Development Kit (JDK) has tools that are required to write Java Programs and uses JRE to execute them. It has a compiler, Java application launcher, and an applet viewer.

So we discussed our java interview questions for intermediate hope these questions will help you with java interview questions for intermediate level now, let’s move on to our Advanced level Java interview questions for 5 years of experience.

Advanced level java interview questions for experienced professionals

Explain JDBC?

Java Database Connectivity (JDBC) is an application programming interface for the programming language Java, which defines how a client may access a database. The method defined by JDBC provides programmatic access from Java to databases that are compliant with the Java DataBase Connectivity Specification (JDBC). Any program or application written in the Java programming language can use JDBC to access a database.

What is Session Management in Java?

Session management is an important part of a web-based application. A session is essentially defined as the random conversation’s dynamic state between the client and the server. The virtual communication channel includes a string of responses and requests from both sides. The popular way of implementing session management is establishing a session ID in the client’s communicative discourse and the server.

What is JCA?

Java Cryptography Architecture gives a platform and provides architecture and application programming interfaces that enable decryption and encryption. cryptography is the science of securing information in data communications. This rich multimedia technology consists of protocols, libraries, formats, algorithms, signature schemes, and a multitude of other components for authentication, confidentiality (encryption is one technique for providing confidentiality), non-repudiation, digital signatures, and random number generation.

Java Interview Questions is a very important aspect of our lives because in every field there is a need for Java and that means it’s quite important to have good knowledge on the topics related to Java sometimes to crack the interview you will be overconfident but that won’t make you stand apart so its best to have those questions in your mind and make yourself ready for these questions.