2.3 Instantiation

Learning Objectives

•Use `new` to instantiate objects.
•Explain what happens in memory when an object is created.
•Store and use a reference to a newly created object.

Introduction

Instantiation is the process of creating an object from a class using the `new` keyword. `new` allocates memory for the object's fields, runs a constructor to initialize them, and returns a reference to the newly created object, which is typically stored in a variable.

Key Concepts

`new ClassName(...)` allocates the object and invokes a matching constructor.

The variable holding the result is a reference to the object, not the object itself.

Multiple references can point to the same object; multiple `new` calls create distinct objects.

Java Syntax

Code Examples

`b = a` makes `b` point to the same object as `a`. Changing `b.name` therefore also changes what `a.name` reports, since there is only one Student object.

Common Mistakes

⚠Forgetting `new`, which is required to create any object (there's no implicit instantiation in Java).
⚠Assuming `Student a = b;` (where `b` is already a Student) creates a new object — it actually just copies the reference, so `a` and `b` point to the same object.

Summary

`new` instantiates a class into an object, running a constructor and returning a reference. Reference assignment copies the reference, not the object.

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