We are going to model a simple 3D point, holding x, y and z.

With a little twist, we will make one mutable and one immutable version of that object.

We want to have the following things:

• All the three components - x, y and z should be private with only getters - getX(), getY(), getZ().
• Our point should have a method, called move(dx, dy, dz), which mutates our point in the following way: x = x + dx, y = y + dy, z = z + dz.
• We want the toString() method to return a string looking like ({x}, {y}, {z})

For example:

var p1 = MutablePoint3d(0, 0, 0);

p1.move(0, 0, -1);

p1.getX() == 0; // true
p1.getY() == 0; // true
p1.getZ() == -1; // true

p1.toString() == "(0, 0, -1)" // true

The twist. We want to create a ImmutablePoint3d object, which behaves the same as MutablePoint3d.

The only difference is that the move(dx, dy, dz) method should return a new ImmutablePoint3d, instead of mutating the instance.

For example:

var p2 = ImmutablePoint3d(0, 0, 0);

var result = p2.move(0, 0, -1);

p2.getX() == 0; // true
p2.getY() == 0; // true
p2.getZ() == 0; // true


result.getZ() == -1; // true

p2.toString() == "(0, 0, 0)" // true
result.toString() == "(0, 0, 0)" // true