Java is widely used across the globe for the development of various web applications and websites. It is estimated that over 3 billion devices all across the world use Java programming. As one of the most popular programming language, the requirement of experienced and eligible developers who is familiar with Java is also increasing day by day. The competition now is very tough and the candidates need to be very familiar with the basic concepts as well as the detailed concepts. The given below are some of the Basic Java coding Interview Questions that the candidates can refer to as they are appearing for a technical interview round.
Top Interview Questions Based on Java
Candidates can expect questions ranging from various difficulties as they appear for a technical interview round. The given below are some of the basic level interview questions that the candidates need to understand and know as they appear for a technical round of Job interview.
What are the differences between C++ and Java?
C++ is not platform-independent; the principle behind C++ programming is “write once, compile anywhere.” In contrast, because the byte code generated by the Java compiler is platform-independent, it can run on any machine, Java programs are written once and run everywhere.
- Languages Compatibility
C++ is a programming language that is based on the C programming language. Most other high-level languages are compatible with C++. Most of the languages of Java are incompatible. Java is comparable to those of C and C++.
- Interaction with the library
It can access the native system libraries directly in C++. As a result, it’s better for programming at the system level. Java’s native libraries do not provide direct call support. You can use Java Native Interface or access the libraries.
C++ distinguishes itself by having features that are similar to procedural and object-oriented languages. The characteristic that sets Java apart is automatic garbage collection. Java doesn’t support destructors at the moment.
- The semantics of the type
Primitive and object types in C++ have the same kind of semantics. The primitive and object classes of Java, on the other hand, are not consistent.
- In the context of Compiler and Interpreter
Java refers to a compiled and interpreted language. In contrast, C++ is only a compiled language. In Java, the source code is the compiled output is a platform-independent byte code. In C++, the source program is compiled into an object code that is further executed to produce an output.
What are the features of the Java Programming language?
- Easy: Java is a language that is considered easy to learn. One fundamental concept of OOP Java has a catch to understand.
- Secured Feature: Java has a secured feature that helps develop a virus-free and tamper-free system for the users.
- OOP: OOP stands for Object-Oriented Programming language. OOP signifies that, in Java, everything is considered an object.
- Independent Platform: Java is not compiled into a platform-specific machine; instead, it is compiled into platform-independent bytecode. This code is interpreted by the Virtual Machine on which the platform runs.
What are the Memory Allocations available in Java?
Java has five significant types of memory allocations.
- Class Memory
- Heap Memory
- Stack Memory
- Program Counter-Memory
- Native Method Stack Memory
What are the differences between Heap and Stack Memory in Java?
Stack is generally used to store the order of method execution and local variables. In contrast, Heap memory is used to store the objects. After storing, they use dynamic memory allocation and deallocation.
Will the program run if we write static public void main?
Yes, the program will successfully execute if written so. Because, in Java, there is no specific rule for the order of specifiers
What is the default value stored in Local Variables?
Neither the Local Variables nor any primitives and Object references have any default value stored in them.
What is an Association?
An Association can be defined as a relationship that has no ownership over another. For example, a person can be associated with multiple banks, and a bank can be related to various people, but no one can own the other.
What do you mean by aggregation?
The term aggregation refers to the relationship between two classes best described as a “whole/part” and “has-a” relationship. This kind is the most specialized version of an association relationship. It contains the reference to another class and is said to have ownership of that class.
What is an object-oriented paradigm?
A Paradigm that is based on the concepts of “Objects.” It contains data and code. Data that is in the form of fields, and regulation, that is in the form of procedures. The exciting feature of this paradigm is that the object’s procedures can access and often modify the data fields themselves.
What is Wrapper Classes in Java?
In Java, when you declare primitive datatypes, then Wrapper classes are responsible for converting them into objects(Reference types).
What is Singleton Classes in Java?
In Java, when you make the constructor of a class private, that particular class can generate only one object. This type of class is popularly known as a Singleton Class.
What is package in Java?
The package is a collective bundle of classes and interfaces and the necessary libraries and JAR files. The use of packages helps in code reusability.
What is JDK? Mention the variants of JDK?
JDK 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.
- JDK Standard Edition
- JDK Enterprise Edition
- JDK Micro Edition
What is the difference between JDK, JRE, and JVM?
JVM 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 has class libraries and other JVM supporting files. But it doesn’t have any tool for java development such as compiler or debugger. 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.
How many types of constructors are used in Java?
There are two types of constructors that are used in Java.
- Parameterized Constructors: Parameterized constructor accepts the parameters with which users can initialize the instance variables. Users can initialize the class variables dynamically at the time of instantiating the class.
- Default constructors: This type doesn’t accept any parameters; rather, it instantiates the class variables with their default values. It is used mainly for object creation.
Why are generics used in Java Programming?
Compile-time type safety is provided by using generics. Compile-time type safety allows users to catch unnecessary invalid types at compile time. Generic methods and classes help programmers specify a single method declaration, a set of related methods, or related types with an available class declaration.
What is Externalizable interface?
The Externalizable interface helps with control over the process of serialization. An “externalisable” interface incorporates readExternal and writeExternal methods.
What are the various directives in JSP?
Directives are instructions processed by JSP Engine. After the JSP page is compiled into a Servlet, Directives set page-level instructions, insert external files, and define customized tag libraries. Directives are defined using the symbols below:
start with “< %@” and then end with “% >”
The various types of directives are shown below:
- Include directive
It includes a file and combines the content of the whole file with the currently active pages.
- Page directive
Page Directive defines specific attributes in the JSP page, like the buffer and error page.
Taglib declares a custom tag library, which is used on the page.
What are the observer and observable classes?
Objects that inherit the “Observable class” take care of a list of “observers.”
When an Observable object gets upgraded, it calls the update() method of each of its observers.
After that, it notifies all the observers that there is a change of state.
The Observer interface gets implemented by objects that observe Observable objects.
What is Session Management in Java?
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.
Explain the term Spring Framework?
Spring is essentially defined as an application framework and inversion of control containers for Java. The spring framework creates enterprise applications in Java. Especially useful to keep in mind that the spring framework’s central features are essentially conducive to any Java application.
How to handle exceptions in Spring MVC Framework?
Spring MVC has two approaches for handling the exceptions:
- Exception handler method: In this kind of exception handling, the user will get the @ExceptionHandler annotation type used to annotate a method to handle exceptions.
- XML Configuration: The user can use the SimpleMappingExceptionResolver bean in Spring’s application file and map the exception.
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