Classes, Objects, and the new Operator Lifecycle

Part of: Java for Beginners › OOP Fundamentals: Classes, Objects, and Attributes

1. The Blueprint and the Buildings: Class vs Objects

A Class is merely the conceptual template written in source code. Objects are the tangible instances living in the Heap at runtime. A single architectural blueprint spawns thousands of autonomous houses.

State Isolation c2.depositar($500);

Cuenta c1 (Lucía): $5.000 (Sin cambios)

Cuenta c2 (Marcos): $120

Cuenta c3 (Elena): $94.000 (Sin cambios)

Each instance encapsulates its own state. Mutating c2 has zero impact on c1 or c3 memory.

2. The 4-Step Lifecycle of new Operator

Persona p = new Persona("Ana", 28); executes in 4 distinct memory phases: Allocation, Zeroing, Constructor invocation, and Pointer assignment.

FASE 1 / 4: RESERVA

Active Phase: 1. Reserva de Memoria

Local variable p: null (sin apuntar)

Heap State: Bloque reservado en 0x5A10

The new keyword requests continuous space in the Heap to accommodate Persona fields.

3. The this Pointer and Variable Shadowing

When a method parameter shares an identical identifier with a field ("nombre = nombre"), the local parameter shadows the field. The this keyword explicitly addresses the current receiving instance.

Syntax Selector

Statement executed: nombre = nombre

Field this.nombre: "Sin Nombre" (Intacto)

Without this, the parameter shadows the field. It copies itself into itself, leaving the instance field untouched.

4. References vs Copies: The Risk of Aliasing

In Java, object variables do NOT hold the object: they hold its memory reference. Writing Persona b = a; creates a second remote control aimed at the exact same Heap address.

Aliasing Mutation Simulator

p1.getNombre(): "Juan"

p2.getNombre(): "Juan"

Objects in Heap: 1 (¡No se duplicó!)

Modifying the object via p2 immediately affects p1 since both reference the exact same memory block.