integrating new koans

Author: matyb

koans/src/PathToEnlightment.xml

@@ -66,6 +66,31 @@
 	  	<Koan name="complicatedCast" />
 	  	<Koan name="complicatedCastWithInterface" />
 	  </Suite>
+	  <Suite class="AboutInheritance">
+	  	<Koan name="differenceBetweenOverloadingAndOverriding" />
+	  	<Koan name="overridenMethodsMayReturnSubtype" 
+	  		lesson="An overridden method may return a subtype of the return type for the method being overridden. Look at the javadoc for java.util.Collection or java.util.List - it will reveal how to eliminate this type cast."/>
+	  </Suite>
+	  <Suite class="AboutConstructors">
+	  	<Koan name="simpleConstructorOrder" />
+	  	<Koan name="complexConstructorOrder" />
+	  </Suite>
+	  <Suite class="AboutMethodPreference">
+	  	<Koan name="methodPreferenceInt" />
+	  	<Koan name="methodPreferenceInteger" />
+	  	<Koan name="methodPreferenceLong" />
+	  	<Koan name="methodPreferenceBoxedLong" />
+	  	<Koan name="methodPreferenceDouble" />
+	  	<Koan name="methodPreferenceMore" />
+	  </Suite>
+	  <Suite class="AboutOperators">
+	  	<Koan name="plusPlusVariablePlusPlus" />
+	  	<Koan name="shortCircuit" />
+	  	<Koan name="fullAnd" />
+	  	<Koan name="shortCircuitAnd" />
+	  	<Koan name="aboutXOR" />
+	  	<Koan name="dontMistakeEqualsForEqualsEquals" />
+	  </Suite>
 	  <Suite class="AboutArrays">
 	  	<Koan name="arraysDoNotConsiderElementsWhenEvaluatingEquality"
 			lesson="Arrays utilize reference equality, they do not consider elements when determining equality."/>

koans/src/beginner/AboutInheritance.java

@@ -1,11 +1,13 @@
 package beginner;
 
-import java.util.ArrayList;
+import static com.sandwich.koan.constant.KoanConstants.__;
+import static com.sandwich.util.Assert.assertEquals;
+
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 
 import com.sandwich.koan.Koan;
-import static com.sandwich.koan.constant.KoanConstants.__;
-import static com.sandwich.util.Assert.assertEquals;
 
 public class AboutInheritance {
 
@@ -25,18 +27,18 @@ public void differenceBetweenOverloadingAndOverriding() {
 	}
 
 	abstract class ParentTwo {
-		abstract public Collection doStuff();
+		abstract public Collection<?> doStuff();
 	}
 
 	class ChildTwo extends ParentTwo {
-		public Collection doStuff() { return null; };
+		public Collection<?> doStuff() { return Collections.emptyList(); };
 	}
 
 	@Koan
 	public void overridenMethodsMayReturnSubtype() {
 		// What do you need to change in order to get rid of the type cast?
 		// Why does this work?
-		ArrayList arraylist = (ArrayList)new ChildTwo().doStuff();
-		assertEquals(arraylist instanceof ArrayList, true);
+		List<?> list = (List<?>)new ChildTwo().doStuff();
+		assertEquals(list instanceof List, __);
 	}
 }