Refactored Chapter 9

Author: RodneyShag

src/Lessons/IntWrapper.java

@@ -0,0 +1,15 @@
+package Lessons;
+
+/* Used in ShallowDeep lesson */
+public class IntWrapper {
+	int value;
+	
+	public IntWrapper(int v){
+		value = v;
+	}
+	
+	@Override
+	public String toString(){
+		return String.valueOf(value);
+	}
+}

src/Lessons/ShallowDeep.java

@@ -0,0 +1,81 @@
+package Lessons;
+
+import java.util.ArrayList;
+
+/*  This is a lesson on how Integer differs from other objects when it comes to copying values
+ * 
+ * - .clone() on an ArrayList<> gives you a new ArrayList. If it's an ArrayList of Integers
+ *   then you get your own deep copy of Integers. If it's an ArrayList of other objects then 
+ *   your ArrayList contains references to the original objects.
+ */
+public class ShallowDeep {
+	public static void main (String [] args){
+		/***********/
+		/* Integer */
+		/***********/
+		System.out.println("************* Integer **************");
+		ArrayList<Integer> array1 = new ArrayList<>();
+		ArrayList<Integer> array2 = new ArrayList<>();
+		
+		Integer a = 2;
+		array1.add(a);
+		array2.add(a);
+		printArrays(array1, array2);
+		
+		a = 88; // changed value of a, but neither array is affected.
+		printArrays(array1, array2);
+		
+		array1.set(0, 99); // changed entry in 1st array. 2nd array remains unaffected.
+		printArrays(array1, array2);
+		
+		array2 = (ArrayList<Integer>) array1.clone(); // cloned 1st array into 2nd array
+		printArrays(array1, array2);
+		
+		array1.set(0, 700); // changed value of element in 1st array, 2nd array remains unaffected
+		printArrays(array1, array2);
+
+		/**************/
+		/* IntWrapper */
+		/**************/
+		System.out.println("************* IntWrapper **************");
+		ArrayList<IntWrapper> array3 = new ArrayList<>();
+		ArrayList<IntWrapper> array4 = new ArrayList<>();
+		
+		IntWrapper four = new IntWrapper(4);
+		array3.add(four);
+		array4.add(four);
+		printArrays2(array3, array4);
+		
+		four.value = 55; // changed value in 1 array, and it changes in other array too
+		printArrays2(array3, array4);
+
+		array3.get(0).value = 99; // changed value in 1st array, changes in 2nd array also
+		printArrays2(array3, array4);
+
+		/* .clone() */
+		ArrayList<IntWrapper> array5 = new ArrayList<>();
+		ArrayList<IntWrapper> array6 = new ArrayList<>();
+		
+		IntWrapper six   = new IntWrapper(6);
+		IntWrapper seven = new IntWrapper(7);
+		array5.add(six);
+		array5.add(seven);
+		printArrays2(array5, array6);
+		
+		array6.addAll((ArrayList<IntWrapper>) array5.clone()); //cloned 1st array into 2nd array
+		printArrays2(array5, array6);
+		
+		array6.get(0).value = 99; // changed value in 1st array, and it changes in 2nd array as well
+		printArrays2(array5, array6);		
+	}
+	
+	private static void printArrays(ArrayList<Integer> array1, ArrayList<Integer> array2){
+		System.out.println("(1st) array = " + array1);
+		System.out.println("(2nd) array = " + array2 + "\n");
+	}
+	
+	private static void printArrays2(ArrayList<IntWrapper> array1, ArrayList<IntWrapper> array2){
+		System.out.println("(1st) array = " + array1);
+		System.out.println("(2nd) array = " + array2 + "\n");
+	}
+}

src/chapter9/Box.java

@@ -1,19 +1,49 @@
 package chapter9;
+
 /* Used in 9.10 */
 public class Box {
 	int width;
 	int height;
 	int depth;
 
-	/* Constructor */
-	Box(int w, int h, int d){
+	/* Constructors */
+	Box (int w, int h, int d){
 		width = w;
 		height = h;
 		depth = d;
 	}
 
+	Box (Box other){
+		width = other.width;
+		height = other.height;
+		depth = other.depth;
+	}
+	
+	/* A box can be placed on 1) an empty platform (that's what the "other == null" is for), or 2) a bigger box (in every dimension) */
 	public boolean canPlaceAbove(Box other){
-		return (other == null) ||(width < other.width && height < other.height && depth < other.depth);
-		// the (other == null) is so the bottom-most box can be placed on anything
+		return (other == null) || ( width < other.width && height < other.height && depth < other.depth);
+	}
+	
+	/* Book didn't have these 2 functions. I think they're needed so Boxes can be hashed correctly */
+	
+	@Override
+	public boolean equals(Object other){
+		if (other == this)
+			return true;
+		if (other == null || !(other instanceof Box))
+			return false;
+		
+		Box otherBox = (Box) other;
+		return width == otherBox.width && height == otherBox.height && depth == otherBox.depth;
+	}
+	
+	@Override
+	public int hashCode(){
+		return 2 * width + 3 * height + 5 * depth;
+	}
+	
+	@Override
+	public String toString() {
+		return "Box (" + width + "," + height + "," + depth + ")";
 	}
 }