// Miya Natsuhara
// 08-05-2019
// CSE142
// TA: Grace Hopper

// An example of value vs. reference semantics.

import java.util.*;

public class ValueReferenceSemantics {
   public static void main(String[] args) {
      int x = 5;
      int y = 7;
      swap(x, y); // this method call has no effect on the values of x and y because ints
                  // are primitive types, and so use value semantics. 
      System.out.println("x is " + x + ", y is " + y);
            
      int[] arr1 = {12, 3, 39, 23, 10, 0};
      int[] arr2 = arr1;
      arr2[0] = 100;
      System.out.println("arr1 is " + Arrays.toString(arr1));
      modify(arr2); // because of reference semantics, the change made in the modify method 
                    // call are reflected when the array is printed out below.
      System.out.println("arr1 is " + Arrays.toString(arr1));
   }
   
   // This method swaps the values of a and b locally, but no changes are reflected at the 
   // call site because of reference semantics. 
   // int a: one of the values to be swapped
   // int b: one of the values to be swapped
   public static void swap(int a, int b) {
      int temp = a;  // we need this temp variable so we "remember" the old value of a
                     // before the value is squashed by putting b's value in a. 
      a = b;
      b = temp;
      System.out.println("a is " + a + ", b is " + b);
   }
   
   // This method takes the given list and puts 99 at index 1 and 666 at index 2. 
   // Because of reference semantics, these changes are reflected at the call site. 
   // int[] list: the list to be modified
   public static void modify(int[] list) {
      list[1] = 99;
      list[2] = 666;
   }
}