r/learnjava • u/jadu2115 • 12d ago
Java Beginners: What Is an Object Actually?
I'm a Java learner and I've been learning Java for the past few months, but I still don't truly understand what an object actually is.
I've watched several YouTube videos and used AI tools to understand it, but I keep getting the same explanation: "An object is nothing but data + code."
I understand the definition, but I still can't visualize or feel what an object actually is when I'm writing Java code.
Could someone explain it in a simple, practical way, preferably with a real world analogy and a small Java example?
I feel like I'm missing one fundamental concept here. Any explanation would be really helpful. Thanks!
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u/protienbudspromax 6d ago
Many ways of looking at it. At its core really an object is a name we give to a region in a computer memory. The object determines what that memory "means" in context of the rest of the program/pc.
When I say the word "house" what do you imagine? The concept of what a house is or your own/friend's house??
A "house" is a concept that has a meaning/some properties. Like a house is generally solid. Has rooms, has doors to allow others to walk between rooms. Can have multiple floors. Can belong to someone or be abandoned. Can be made of wood, cement, tiles etc. Can have a property of "electricity"/"storage" etc.
These are all concepts. And tells us what a house is and what things a house have. When I simply say "house". Which "house" do I mean specifically? Your house? My house? The whitehouse? The concept of a house dont care about that.
That is like a class. It is a description. A definition of what a house is. It itself is not a house. It itself is a description.
But an actual house? That is a physical thing that can have some or all properties defined by the description of a house. It is a real actual "version" of the concept of a house.
That is the main difference. A class is not the object itself, but the description of it. And anything that can be described to have the properties of the class is an object of that class.
In practice we mainly use it in programming to avoid code duplication (cuz say you write a class for a vehicle, and all vehicles can move) so if you define more types of vehicle then you can simply extend vehicle, or maybe create a trait/interface that defines "moveable" property and add that property to any other type. Like a cycle is also "moveable" thus share some functionality.
The other primary functionality is abstraction. If you know that a vehicle can move. Then you would know that if I give you any type of vehicle it likely can move. But you may not be told "how" it can move. Just that it moves. Being able to move is a property of the thing it is.
That hiding the "how" turns out can be pretty useful. But for now this should be enough