Java Interview Question and Answers
Java Interview Question and Answers: Java is a high-level, object-oriented programming language that was first released in 1995 by Sun Microsystems (now owned by Oracle Corporation). It is designed to be platform-independent, which means that Java code can run on any operating system or hardware that supports a Java Virtual Machine (JVM). Here we are Providing Important Java Interview Question and Answers.
What is Java?
Answer: Java is a high-level, object-oriented, and platform-independent programming language that was developed by James Gosling and his team at Sun Microsystems. Java code is compiled into byte code, which can be run on any Java Virtual Machine (JVM) regardless of the operating system.
What are the features of Java?
Answer: Java has many features, including:
Object-oriented programming, Platform independence, Automatic memory management, Exception handling, Multi-threading, Robustness and security and Garbage collection
What is the difference between JDK, JRE, and JVM?
Answer: JDK (Java Development Kit) is a software development kit used to develop Java applications. It includes the Java Runtime Environment (JRE), the Java Compiler, and other development tools.
JRE (Java Runtime Environment) is an environment for running Java applications. It includes the JVM (Java Virtual Machine) and the core classes of the Java standard library.
JVM (Java Virtual Machine) is a virtual machine that executes Java byte code. It is the cornerstone of the Java platform.
What is the difference between an abstract class and an interface?
Answer: An abstract class is a class that cannot be instantiated, and can have both abstract and non-abstract methods. It can also have instance variables and constructors. A subclass of an abstract class must implement all the abstract methods of the superclass.
An interface is a contract between a class and the outside world. It only contains abstract methods, constants, and nested types. A class that implements an interface must provide an implementation for all the methods declared in the interface.
What is the difference between a stack and a queue?
Answer: A stack is a data structure that follows the Last-In-First-Out (LIFO) principle, where the last element added to the stack is the first element to be removed. It has two main operations: push (adds an element to the top of the stack) and pop (removes the top element from the stack).
A queue is a data structure that follows the First-In-First-Out (FIFO) principle, where the first element added to the queue is the first element to be removed. It has two main operations: enqueue (adds an element to the end of the queue) and dequeue (removes the first element from the queue).
What is the difference between an ArrayList and a LinkedList?
Answer: An ArrayList is an implementation of the List interface that is backed by an array. It allows random access to elements and is more efficient when accessing elements by index. However, it is less efficient when inserting or deleting elements in the middle of the list.
A LinkedList is an implementation of the List interface that is backed by a doubly-linked list. It is more efficient when inserting or deleting elements in the middle of the list, but less efficient when accessing elements by index.
What is a thread?
Answer: A thread is a lightweight process that can run concurrently with other threads within the same program. Threads share the same memory space and can communicate with each other through shared objects. Java supports multithreading, which means that a single program can have multiple threads running simultaneously.
What is synchronization in Java?
Answer: Synchronization is a mechanism in Java that allows multiple threads to access a shared resource in a mutually exclusive way. This is achieved by using the synchronized keyword to mark a block of code or a method as synchronized. Only one thread can execute a synchronized block or method at a time, while other threads are blocked until the synchronized block or method is released.
What is exception handling in Java?
Answer: Exception handling is a mechanism in Java that allows a program to handle runtime errors in a controlled way. When an exception occurs, the JVM creates an exception object and throws it to the calling method.
What is the Java Virtual Machine (JVM)?
Answer: The Java Virtual Machine (JVM) is a virtual machine that executes Java byte code. It is the cornerstone of the Java platform and provides a platform-independent environment for running Java programs. The JVM is responsible for loading and executing Java programs, managing memory, and providing security and other services. Java programs are compiled into byte code, which can be run on any JVM regardless of the operating system.
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