import java.util.*;

// CSE 143, Summer 2016
//
// A mysterious program used to play with reference semantics.
// I encourage you to change things around and see what you get!
public class ReferenceMystery {
  public static void main(String[] args) {
    // new = creating new list!
    ArrayList<String> groceries = new ArrayList<String>();
    groceries.add("cookies");
    groceries.add("milk");
    groceries.add("pizza");
    groceries.add("ice cream");
    groceries.add("tomato");
    
    System.out.println("food: " + groceries);
    System.out.println();
    
    // creating a REFERENCE to the same list, groceries
    // We now have two variables, groceries and sameGroceries,
    // that reference the same ArrayList<String>.
    List<String> sameGroceries = groceries;
    sameGroceries = groceries;
    
    checkGroceries(sameGroceries);
    
    System.out.println("food: " + groceries);

    // Here are more cases we talked about in class.

    // This uses an ArrayList constructor to copy "groceries".
    // They no longer reference the same list. Any changes made
    // to otherGroceries will not be reflected in groceries.
    List<String> otherGroceries = new ArrayList<String>(groceries);

    // In another attempt to copy the list, we tried this. This however
    // does something really never desired: we create a new list,
    // and immediately lose it by changing the REFERENCE of yetMoreGroceries.
    // In the end, yetMoreGroceries just references groceries, and
    // we've lost forever the reference to the new Arraylist<String> we
    // created.
    List<String> yetMoreGroceries = new ArrayList<String>();
    yetMoreGroceries = groceries;
  }

  // Checks all groceries to make sure you're not eating too
  // much junk food!
  // pre : groceries != null
  // post: removes junk food that isn't good for you
  public static void checkGroceries(List<String> groceries) {
    for (int i = 0; i < groceries.size(); i++) {
      if (groceries.get(i).equals("cookies")) {
        // you can't have cookies
        groceries.remove(i);
      }
    }
    // You can have Joe Joe's. They're just as good.
    groceries.add("Joe Joe's");
  }
}