What does the key word new do?

When learning Java, one of the fundamental concepts to grasp is memory allocation. This process is crucial for creating new objects and ensuring they have a dedicated space in the computer's memory to store data and facilitate operations.

In Java, memory is mainly divided into two areas: the stack and the heap. The stack is where method invocations and local variables reside, while the heap is a larger pool of memory where Java objects live. When you use the 'new' keyword in Java, you are directing your program to allocate space in the heap for a new object.

How Does the 'new' Keyword Allocate Memory?

Simply put, the 'new' keyword signals the Java Virtual Machine (JVM) to reserve a chunk of heap memory for the object you're creating. This space is just enough to hold all the instance variables and data structures the object will need. Unlike languages such as C++, Java manages this memory for you—meaning you don't have to worry about deallocating memory manually; Java's garbage collector automatically frees up space from objects that are no longer in use.

After memory is allocated, the next step in creating an object is initialization. Object initialization is the process of assigning values to the properties of an object at the time of its creation.

In Java, object initialization is typically tied to constructors, which are special methods called when an object is created. They have the same name as the class and contain code that sets the initial state of an object.

Default Values and Initialization

When an object is created without any constructor being specified, Java provides a default constructor that initializes all instance variables to their default values (such as 0 for integers, 'null' for object references, and so on). If you do define a constructor, you can set the initial values to whatever is appropriate for your class, as seen in the 'Person' class example in our exercise.

Java constructors play a vital role in instance creation; they are the heart of object initialization in Java.

A constructor resembles a method but is unique because it has no explicit return type and its name must match the class name exactly. Its primary purpose is to construct the object by setting initial values for the object's properties.

Different Types of Constructors

There are different types of constructors in Java:

• Default Constructor: Automatically provided by Java if no other constructors are explicitly defined. Sets fields to default values.
• Parameterized Constructor: Allows passing parameters and assigning them to the object's fields, thereby giving flexibility during object creation.
• Copy Constructor: Takes another object of the same class as a parameter and copies its values.

Constructors can be overloaded, which means you can have multiple constructors in the same class as long as they have different parameter lists. This provides flexibility and allows for different ways of initializing objects depending on the context.

Object-oriented programming (OOP) is a programming paradigm that is based on the concept of objects, which can contain data, in the form of fields, and code, in the form of procedures or methods.

In OOP, programs are designed by making them out of objects that interact with one another. It's all about creating reusable codes and simulating real-world entities through classes and objects. It stands on the four main principles: encapsulation, inheritance, abstraction, and polymorphism.

Brief Overview of OOP Principles

• Encapsulation: Enclosing data and methods within classes, and using access modifiers to control the visibility and accessibility of components.
• Inheritance: Deriving new classes from existing ones, thereby facilitating code reusability and the creation of a hierarchical classification.
• Abstraction: Hiding complex implementation details and showing only the necessary features of objects.
• Polymorphism: Allowing entities to take on multiple forms, enabling objects to be treated as instances of their parent class rather than their actual class.

Understanding these principles is fundamental to effectively using object-oriented features in Java, which includes the 'new' keyword, as part of object creation and management.