Basic Java Viva Questions And Answers Pdf
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- Java interview questions for 2 years experience
- 100+ Java Interview Questions You Must Prepare In 2021
- Java Interview Questions and Answers
Java interview questions for 2 years experience
Java has been a perennial contributor to the software development domain. It is not only necessary to learn and master Java skills but also to practice these skills in real-time. In this article, we bring you, some of the most sought after Java Interview Questions that will help you ace major interview processes and help test your skills and knowledge at its absolute. You can access various programming and technical courses on Great Learning Academy and get your free certificates.
Java is a general-purpose programming language that is class-based, object-oriented and is very popular. Install Java through command prompt so that it can generate necessary log files to troubleshoot the issue. Threads allows a program to operate more efficiently by doing multiple things at the same time. Threads can be used to perform complicated tasks in the background without interrupting the main program. If the version is old or you get the error java: Command not found, then the path is not properly set.
Enumeration means a list of named constant. In Java, enumeration defines a class type. An Enumeration can have constructors, methods and instance variables. It is created using enum keyword. Each enumeration constant is public, static and final by default.
Even though enumeration defines a class type and have constructors, you do not instantiate an enum using new. Enumeration variables are used and declared in much a same way as you do a primitive variable. The process by which one class acquires the properties data members and functionalities methods of another class is called inheritance. The aim of inheritance is to provide the reusability of code so that a class has to write only the unique features and rest of the common properties and functionalities can be extended from another class.
Child Class: The class that extends the features of another class is known as child class, sub class or derived class. Parent Class: The class whose properties and functionalities are used inherited by another class is known as parent class, super class or Base class. Objects are the building blocks of Object-Oriented Programming. An object contains some properties and methods. We can hide them from the outer world through access modifiers.
We can provide access only for required functions and properties to the other programs. This is the general procedure to implement abstraction in OOPS. The idea behind encapsulation is to hide the implementation details from users.
If a data member is private it means it can only be accessed within the same class. No outside class can access private data member variable of other class. However if we setup public getter and setter methods to update for example void setName String Name and read for example String getName the private data fields then the outside class can access those private data fields via public methods.
Collections are like containers that group multiple items in a single unit. For example, a jar of chocolates, list of names, etc. Collections are used in every programming language and when Java arrived, it also came with few Collection classes — Vector, Stack, Hashtable, Array. It includes all Java packages, classes, and interfaces, along with their methods, fields, and constructors.
These pre-written classes provide a tremendous amount of functionality to a programmer. Instead, the member belongs to the class itself. As a result, you can access the static member without first creating a class instance. A package in Java is used to group related classes.
Think of it as a folder in a file directory. We use packages to avoid name conflicts, and to write a better maintainable code. It can have abstract methods methods without body as well as concrete methods regular methods with body. A normal class non-abstract class cannot have abstract methods. A method is a block of code which only runs when it is called.
You can pass data, known as parameters, into a method. Methods are used to perform certain actions, and they are also known as functions. A class—the basic building block of an object-oriented language such as Java—is a template that describes the data and behaviour associated with instances of that class. When you instantiate a class you create an object that looks and feels like other instances of the same class. The data associated with a class or object is stored in variables; the behaviour associated with a class or object is implemented with methods.
String is a sequence of characters, for e. In java, string is an immutable object which means it is constant and cannot be changed once it has been created. When an error occurs within a method, the method creates an object and hands it off to the runtime system. The object, called an exception object, contains information about the error, including its type and the state of the program when the error occurred.
Creating an exception object and handing it to the runtime system is called throwing an exception. After a method throws an exception, the runtime system attempts to find something to handle it. The list of methods is known as the call stack.
Java supports multiple inheritance through interfaces only. A class can implement any number of interfaces but can extend only one class.
Multiple inheritance is not supported because it leads to a deadly diamond problem. The singleton design pattern is used to restrict the instantiation of a class and ensures that only one instance of the class exists in the JVM. In other words, a singleton class is a class that can have only one object an instance of the class at a time per JVM instance. An array is a container object that holds a fixed number of values of a single type.
The length of an array is established when the array is created. After creation, its length is fixed. This section discusses arrays in greater detail. Illustration of an array as 10 boxes numbered 0 through 9; an index of 0 indicates the first element in the array. An array of 10 elements.
Each item in an array is called an element, and each element is accessed by its numerical index. As shown in the preceding illustration, numbering begins with 0. The 9th element, for example, would therefore be accessed at index 8. Java garbage collection is an automatic process. The programmer does not need to explicitly mark objects to be deleted.
The garbage collection implementation lives in the JVM. Each JVM can implement garbage collection however it pleases; the only requirement is that it meets the JVM specification. It offers a robust and mature set of garbage collection options.
Encapsulation in Java is a mechanism of wrapping the code and data variables acting on the data methods together as a single unit. In encapsulation, the variables of a class will be hidden from other classes and can be accessed only through the methods of their current class.
A Java virtual machine JVM is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. Java is a powerful general-purpose programming language. It is used to develop desktop and mobile applications, big data processing, embedded systems, and so on.
According to Oracle, the company that owns Java, Java runs on 3 billion devices worldwide, which makes Java one of the most popular programming languages. HashMap in Java works on hashing principles. It is a data structure which allows us to store object and retrieve it in constant time O 1 provided we know the key. In hashing, hash functions are used to link key and value in HashMap.
Open a command prompt window and go to the directory where you saved the java program HelloWorld. You will be able to see the result printed on the window. Bytecode is the compiled format for Java programs. Bytecode files generally have a. To create an enum, use the enum keyword instead of class or interface , and separate the constants with a comma.
Dao is a simple java class which contains JDBC logic. Business applications almost always need access to data from relational or object databases and the Java platform offers many techniques for accessing this data. For example, Connected Device Configuration profiles require Java runtimes on mobile telephones to support the Abstract Window Toolkit.
Frameworks are large bodies usually many classes of prewritten code to which you add your own code to solve a problem in a specific domain. Perhaps you could say that the framework uses your code because it is usually the framework that is in control. When the pop-out menu appears select Configure Java, located in the Apps section. A Java variable is a piece of memory that can contain a data value. A variable thus has a data type.
Data types are covered in more detail in the text on Java data types. Variables are typically used to store information which your Java program needs to do its job.
100+ Java Interview Questions You Must Prepare In 2021
The main distinction between fail-fast and fail-safe iterators is whether or not the collection can be modified while it is being iterated. Fail-safe iterators allow this; fail-fast iterators do not. Fail-fast iterators operate directly on the collection itself. During iteration, fail-fast iterators fail as soon as they realize that the collection has been modified i. Fail-safe iterates operate on a cloned copy of the collection and therefore do not throw an exception if the collection is modified during iteration.
Java has been a perennial contributor to the software development domain. It is not only necessary to learn and master Java skills but also to practice these skills in real-time. In this article, we bring you, some of the most sought after Java Interview Questions that will help you ace major interview processes and help test your skills and knowledge at its absolute. You can access various programming and technical courses on Great Learning Academy and get your free certificates. Java is a general-purpose programming language that is class-based, object-oriented and is very popular.
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Dear readers, these Java Interview Questions have been designed especially to get during your interview, normally questions start with some basic concept of and later they continue based on further discussion and what you answer −.
Java Interview Questions and Answers
Download PDF We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. The following list contains important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview. This detailed guide of interview questions for Java Programming will help you to crack your Job interview easily.