•x = y    means                                                          
 “make the value of x the value of y !”
 •Example (primitive types)
 –int
 y = 6; // declare y, initialize value
 –int
 x;     // declare x
 –x
 = y; // copy content of box y into box x
 •For reference types, x = y means arrow in x now
 points to the same place as arrow in y.
 •x = y   is not the same as y
 = x                    
 •This makes mathematicians
 unhappy