Constructors: Building Objects the Right Way

Constructors play a critical role in Java by ensuring every object is properly set up before you use it. When you create a new object with the new keyword, the Java Virtual Machine (JVM) steps in to handle several important tasks behind the scenes:

• Allocates memory for the new object on the heap;
• Sets all instance variables to their default values (such as 0 for numbers, false for booleans, and null for object references);
• Calls the constructor method, which runs your custom initialization code.

Inside a constructor, you usually assign values to instance variables, ensuring your object starts life in a valid state. If your class extends another class, the JVM automatically calls the superclass constructor first, either implicitly or as the first line in your constructor using super(). This guarantees that all inherited fields are set up before your own class’s fields.

After the constructor completes, the JVM returns a reference to the newly created object. This reference is what you use to interact with the object in your code. If you assign the object to a variable, the variable holds this reference, not the object itself. When you pass the object to a method or another variable, you are actually passing the reference, allowing multiple variables to point to the same object in memory.

Understanding the constructor process helps you write safer and more predictable code, ensuring your objects are always ready for use as soon as they are created.