Java is one of the most widely used programming languages in the world, and it's used in a variety of applications, from mobile apps to web applications to enterprise systems. If you're preparing for a Java interview, it's important to be well-versed in the language's fundamentals and to have a good understanding of the various libraries and frameworks that are commonly used in Java development.
What is Java?
Java is a high-level, object-oriented programming language that was developed by Sun Microsystems in the mid-1990s. It's designed to be platform-independent, which means that Java code can run on any platform that has a Java Virtual Machine (JVM) installed. Java is used for a wide range of applications, including web development, mobile app development, and enterprise software development.
What is the difference between a class and an object in Java?
In Java, a class is a blueprint for creating objects. It defines the properties and methods that an object of that class will have. An object, on the other hand, is an instance of a class. When you create an object, you're creating a specific instance of that class, with its own set of values for the properties defined by the class.
What is inheritance in Java?
Inheritance is a mechanism in Java that allows you to create a new class that is a modified version of an existing class. The new class inherits all the properties and methods of the original class, but you can also add new properties and methods or modify existing ones. Inheritance is a powerful tool for creating code that is reusable and maintainable.
What is a constructor in Java?
A constructor is a special method that is called when an object of a class is created. Its purpose is to initialize the properties of the object to their initial values. Constructors can have parameters, which allows you to specify the initial values of the object's properties when the object is created.
What is a package in Java?
A package in Java is a way of organizing related classes and interfaces into a single unit. It helps to avoid naming conflicts and makes it easier to manage large projects. Packages can be nested, which allows you to create a hierarchy of related packages.
What is a thread in Java?
A thread is a separate path of execution in a Java program. A program can have multiple threads, each of which can run concurrently with the others. Threads are used for tasks that need to run in the background, such as updating a user interface or processing data.
What is the difference between a list and a set in Java?
In Java, a list is an ordered collection of elements, while a set is an unordered collection of unique elements. This means that a list can contain duplicate elements, while a set cannot. Lists are typically used when you need to maintain the order of the elements, while sets are used when you need to ensure that each element is unique.
What is the difference between a checked and an unchecked exception in Java?
In Java, a checked exception is a type of exception that must be declared in the method signature or handled in a try-catch block. This means that the compiler will enforce that the exception is handled in some way. An unchecked exception, on the other hand, is a type of exception that does not need to be declared or handled. Unchecked exceptions are typically used for programming errors, such as null pointer exceptions.
What is the Java Collections Framework?
The Java Collections Framework is a set of classes and interfaces that provides a unified way of working with collections of objects in Java. It includes classes like ArrayList, LinkedList, HashSet, and TreeMap, which provide different.