// Helene Martin, CSE 142
// Demonstrates the difference between value semantics (primitive types) and 
// reference semantics (object types).

// In Java, primitive types use value semantics so assignment results 
// in copying a value. Object types use reference semantics so assignment
// results in copying a REFERENCE (memory location) to an object.
import java.util.*;

public class ValueReferenceSemantics {
   public static void main(String[] args) {
      int a = 7;
      int b = 35;
	   
      // this call has no effect because integers are
      // copied when passed into a method (value semantics)
      swap(a, b);
	    
      System.out.println(a + " " + b);
      
      // there is only one array but values1 and values2 are 
      // both references to that array (reference semantics)
      int[] values1 = {56, 23, 21, -11, 67};
      int[] values2 = values1;
      
      // changing a value from one of the references is visible from
      // both references
      values1[0] = 555;
      System.out.println(Arrays.toString(values1));
      System.out.println(Arrays.toString(values2));
      
      swapArr(values1);
      System.out.println(Arrays.toString(values1));
      System.out.println(Arrays.toString(values2));      
   }
   
   // Swaps the first two elements in an array
   public static void swapArr(int[] arr) {
      int temp = arr[0];
      arr[0] = arr[1];
      arr[1] = temp;
   }
   
   // Attempts to swap two integers but because of value semantics,
   // the change only happens locally to the method
   public static void swap(int a, int b) {
      int temp = a;
      a = b;
      b = temp;
   }
}