The Java + Spring Boot Blueprint(Blog 14 — Java Classes-Part 2 (Java Generics — From Problem to Powerful Design))

“Generics didn’t start as a feature. They started as a problem developers were tired of solving again and again.”

It All Started With a Simple Need

Imagine you’re building a simple container class — something that can store a value and return it.

The most straightforward way (before generics existed) looked like this:

class Box {
    Object value;

    void set(Object value) {
        this.value = value;
    }
    Object get() {
        return value;
    }
}

At first glance, this feels smart.

Why?

Because Object in Java is the parent of every class. That means this Box can store anything — a String, an Integer, or even your custom objects.

Box box = new Box();
box.set("Hello");
box.set(10);

So far, so good.

The Hidden Problem

The problem doesn’t appear when storing data — it appears when retrieving it.

String str = (String) box.get();

You are forced to typecast.