Introduction to OOP

Chapter 12: Implications of substitution:

Meaning of Assignment?

What does it mean whan an instance of a class is assigned to another variable?

class Box {
	public int value;
}

Box x = new Box();
x.value = 7;
Box y = x;
y.value = 12;  // what is x.value?

Two possibilities:

Copy semantics. x and y are independent of each other, a change in one has no effect on the other.
Pointer semantcs. x and y refer to the same object, and hence a change in one will alter the other.