How does data copying occur when passing data to a function or method by value?

When passing data to a function or method by value, a copy of the passed value is created. This means that inside the function, a separate copy of the data operates, and changes to this copy do not affect the original outside the function.

For example, if a primitive type (int, float, etc.) is passed to a function, the function receives a copy of this value. If the parameter is modified inside the function, the original value remains unchanged.

In the case of objects in Java and Android, passing by value means that a reference to the object is copied, not the object itself. That is, the address of the object in memory is copied, and inside the function, the object's state can be changed, but the reference itself cannot be changed to point to another object.

Example in Java:

void modify(int x) {
    x = 10; // local copy is changed
}

void modifyObject(MyObject obj) {
    obj.value = 10; // object state is changed
}

int a = 5;
modify(a);
// a is still 5

MyObject o = new MyObject();
o.value = 5;
modifyObject(o);
// o.value is now 10

Thus, when passing by value, either the value itself (primitives) or the reference to the object (objects) is copied.