When beginners learn object-oriented programming (OOP), the term “object state” can be confusing. In real life, the state of an object usually describes its physical or functional condition. For example, if a glass is broken, its state is “broken.” However, in programming, state means something different.

Let’s understand what object state really means in code.

Object State in Real Life vs. Programming

In real life, an object’s state is its current condition. For example:

• A glass can be intact or broken.
• A car can be functional or not working.
• A lamp can be on or off.

But in programming, the state of an object is the values of its fields (variables) at a specific moment. In other words, an object’s state is all the data that describe it.

Code Example

Let’s take a simple Car class:

class Car {
    String brand;
    int year;
}

Now, we create an object:

Car car1 = new Car();
car1.brand = "Volvo";
car1.year = 2002;

What is the state of car1?

• brand = "Volvo"
• year = 2002

This represents the object’s state! Even though we didn’t include a field for “functional or not,” the object still has a state because it holds data.

Now, let’s add a field that indicates whether the car is functional:

class Car {
    String brand;
    int year;
    boolean isFunctional; // is the car functional?
}

We create another car object:

Car car2 = new Car();
car2.brand = "Volvo";
car2.year = 2002;
car2.isFunctional = false; // the car is not working

Now, the state of car2 includes:

• brand = "Volvo"
• year = 2002
• isFunctional = false (the car is not working)

Both versions of the Car class (with and without isFunctional) have an object state.

Key Takeaways

1. An object’s state in programming is all its current data. Every field (variable) contributes to the state.
2. State in programming is not the same as physical condition. Fields store any information important for the program’s logic.
3. If an object has data, it has a state. Even if a class only has brand and year, the object still has a state.

Final Thoughts

In programming, an object’s state is simply the set of values stored in its fields at a given moment. It does not have to describe the physical state of the object as we understand it in real life. Instead, it represents all the data that define the object at that point in time.