Parameter passing mechanism in Java

- Java only supports call-by-value 

- When a function (caller) passes an object reference to another
  function (callee), it passes a reference by value.

  See MemoryRep.java in Lecture 8 for examples.
  Every function that you see in MemoryRep uses call-by-value, i.e.,
  a copy of a value is passed when a value is passed from a caller to
  a callee.

  If Java allows call-by-reference, the semantics that you get would
  be quite different.  For example, if it was done by
  call-by-reference, the changes that you make in swap for x and y
  would affect the values of i and j in the first call of swap in
  main of MemoryRep.java.

  Similarly, for the cut function and the cut call in main.
  That is why I said Java passes a reference by value, which is
  quite different than saying Java supports a call-by-reference
  parameter passing mechanism.

  If you don't want to worry about call-by-reference, that is fine.
  I just wanted to mention this for those who might be interested.
  Or, you might hear someone saying that Java also supports
  call-by-reference at some point somewhere and you will know that
  that person is saying something that is incorrect.

- When we called swap2 with an array as an argument in the main of
  MemoryRep.java, the changes that you make inside the array in swap2
  survives the function call.  That is, the changes that you make in
  the array from swap2 are visible from the main as well.  This looks
  much like what call-by-reference would do, but technically it is
  still a call-by-value.  The distinction between call-by-value and
  call-by-reference is not that important for us.  You will learn them
  in more detail when you take CSE 216.  For us for now it is
  important how changes that you make in a callee affects the values
  in the caller when you pass a primitive type value versus when you
  pass an object type value.  Remember that an array is an object!