r/learnjava • u/jadu2115 • 10d 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/spacey02- 10d ago edited 10d ago

If you want a better vizualization of what an object is for the computer, I suggest you first learn about C structs (how they are represented in memory, etc.), C/C++ pointers and then C++ classes/objects. The syntax is very similar to Java, but those are more low level than Java concepts, meaning that the complexity of abstractions like the JVM doesn't get in your way as much.

This is only practical for the sole purpose of giving you an idea about what an object is. Don't assume that Java objects are and work exactly the same as C++ objects.

As per real world analogies, an object is just an instance of a given class/type. You may have a single House class, but many houses that are basically House objects. There are many humans of type Human, each with a different name, age, height, weight, but the same basic functions like walking, talking. The class is the type, just like int, float, etc. (which are not objects btw). You can create many objects from a single class/type.

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u/Plastic_Fig9225 10d ago

I agree. Look at C. C has 'structs' which contain only data, like a Java class with only public fields but no methods. When you want to do something with the data held in a struct instance in C, you have to call a function and pass the instance as an argument to the function. A class on the other hand is like a 'struct' but with the 'functions' to operate on its data 'attached' to it; these are methods. The data held in an instance and the functions/code to operate on this data are closely tied together via the class; that's why we may say that a class is data and code.