Here are some Java basic interview questions and their answers:
Java is a high-level, object-oriented programming language that was designed to be platform-independent and easily portable.
JDK stands for Java Development Kit and includes tools for developing and compiling Java code. JRE stands for Java Runtime Environment and is used to run Java applications. JVM stands for Java Virtual Machine and is responsible for executing Java bytecode.
Some main features of Java include platform independence, object-oriented programming, multithreading, automatic garbage collection, and built-in exception handling.
An object is an instance of a class that has its own set of properties and methods.
A class is a blueprint or template for creating objects that defines the properties and methods of the object.
Inheritance is a feature of object-oriented programming that allows a new class to be based on an existing class, inheriting its properties and methods.
Polymorphism is a feature of object-oriented programming that allows objects of different classes to be treated as if they are of the same type.
Encapsulation is a feature of object-oriented programming that involves hiding the implementation details of an object and providing access to its properties and methods only through a public interface.
Abstraction is a feature of object-oriented programming that involves defining the essential characteristics of an object and ignoring the non-essential details.
An abstract class can have both concrete and abstract methods, while an interface can only have abstract methods. Additionally, a class can only extend one abstract class, but can implement multiple interfaces.
A compiler translates source code into machine code, while an interpreter executes code directly.
A String is an immutable sequence of characters, while a StringBuilder and StringBuffer are mutable sequences of characters. StringBuilder is not thread-safe, while StringBuffer is thread-safe.
A package is a collection of related classes and interfaces that provide a namespace for organizing code and avoiding naming conflicts.
A constructor is a special method used to initialize an object when it is created.
An instance variable is associated with a specific instance of a class and has a different value for each instance, while a static variable is associated with the class itself and has the same value for all instances of the class.