Minor updates based on comments from Maurice

LambdaLab/test/solutions/A_Lambdas.java

@@ -59,8 +59,12 @@ public class A_Lambdas {
     }
 
     /**
-     * Write a method reference that is a predicate
-     * that tests whether a string is empty.
+     * Write an unbound method reference that is a predicate
+     * that tests whether a string is empty. An unbound method
+     * reference has a class name on the left-hand side of the ::
+     * operator:
+     *
+     *     classname::methodname
      */
     @Test
     public void a_predicate3() {
@@ -150,7 +154,7 @@ public class A_Lambdas {
     }
 
     /**
-     * Write a method reference that converts the
+     * Write an unbound method reference that converts the
      * given string to upper case.
      */
     @Test
@@ -222,7 +226,7 @@ public class A_Lambdas {
     }
 
     /**
-     * Write a method reference that clears the given list.
+     * Write an unbound method reference that clears the given list.
      */
     @Test
     public void c_consumer3() {
@@ -287,7 +291,7 @@ public class A_Lambdas {
     }
 
     /**
-     * Write a method reference that returns a new, empty StringBuilder.
+     * Write an unbound method reference that returns a new, empty StringBuilder.
      */
     @Test
     public void d_supplier3() {
@@ -311,7 +315,7 @@ public class A_Lambdas {
         BiFunction<String, String, String> bifunc = (s1, s2) -> s1 + s2 + s1;
         //ENDREMOVE
 
-        assertEquals("abcdefabc", bifunc.apply("abc", "def"));
+        assertEquals("FirstSecondFirst", bifunc.apply("First", "Second"));
     }
 
     /**
@@ -326,12 +330,12 @@ public class A_Lambdas {
         BiFunction<String, String, Integer> bifunc = (s1, s2) -> s1.indexOf(s2);
         //ENDREMOVE
 
-        assertEquals((Integer)3, bifunc.apply("abcdefghi", "def"));
-        assertEquals((Integer)(-1), bifunc.apply("abcdefghi", "xyz"));
+        assertEquals(3, bifunc.apply("abcdefghi", "def").intValue());
+        assertEquals(-1, bifunc.apply("abcdefghi", "xyz").intValue());
     }
 
     /**
-     * Write a method reference that returns the index of
+     * Write an unbound method reference that returns the index of
      * the first occurrence of the second string within the first string,
      * or -1 if the second string doesn't occur within the first string.
      */
@@ -342,9 +346,18 @@ public class A_Lambdas {
         BiFunction<String, String, Integer> bifunc = String::indexOf;
         //ENDREMOVE
 
-        assertEquals((Integer)3, bifunc.apply("abcdefghij", "def"));
-        assertEquals((Integer)(-1), bifunc.apply("abcdefghij", "xyz"));
+        assertEquals(3, bifunc.apply("abcdefghij", "def").intValue());
+        assertEquals(-1, bifunc.apply("abcdefghij", "xyz").intValue());
     }
+    // Hint:
+    // <editor-fold defaultstate="collapsed">
+    // The String.indexOf() method is called on the receiver and passes
+    // a single argument. This is like a method that has two arguments.
+    // The receiver becomes the first argument to the BiFunction, and
+    // the argument to indexOf() becomes the second argument to the
+    // BiFunction.
+    // </editor-fold>
+
 
     /**
      * Write a lambda expression that appends the 'suffix'
@@ -379,9 +392,9 @@ public class A_Lambdas {
         Function<String, Integer> func = s -> "abcdefghij".indexOf(s);
         //ENDREMOVE
 
-        assertEquals((Integer)2, func.apply("cde"));
-        assertEquals((Integer)4, func.apply("efg"));
-        assertEquals((Integer)(-1), func.apply("xyz"));
+        assertEquals(2, func.apply("cde").intValue());
+        assertEquals(4, func.apply("efg").intValue());
+        assertEquals(-1, func.apply("xyz").intValue());
     }
     // Hint:
     // <editor-fold defaultstate="collapsed">
@@ -392,7 +405,14 @@ public class A_Lambdas {
      * Write a bound method reference that takes a string argument
      * and returns the index of that argument into the string
      * "abcdefghij", or that returns -1 if the string argument
-     * doesn't occur.
+     * doesn't occur. A bound method reference has an instance,
+     * or an expression that evaluates to an instance, on the left-hand
+     * side of the :: operator:
+     *
+     *     myObject::methodname
+     *
+     * This is in contrast to an unbound method reference, which has
+     * a classname on the left-hand side of the :: operator.
      */
     @Test
     public void g_boundMethodRef2() {
@@ -401,9 +421,9 @@ public class A_Lambdas {
         Function<String, Integer> func = "abcdefghij"::indexOf;
         //ENDREMOVE
 
-        assertEquals((Integer)2, func.apply("cde"));
-        assertEquals((Integer)4, func.apply("efg"));
-        assertEquals((Integer)(-1), func.apply("xyz"));
+        assertEquals(2, func.apply("cde").intValue());
+        assertEquals(4, func.apply("efg").intValue());
+        assertEquals(-1, func.apply("xyz").intValue());
     }
     // Hint:
     // <editor-fold defaultstate="collapsed">

LambdaLab/test/solutions/B_Comparators.java

@@ -20,7 +20,7 @@ import model.Person;
  * getters.
  */
 public class B_Comparators {
-    
+
     final Person michael = new Person("Michael", "Jackson", 51);
     final Person rod = new Person("Rod", "Stewart", 71);
     final Person paul = new Person("Paul", "McCartney", 74);
@@ -118,7 +118,7 @@ public class B_Comparators {
     // <editor-fold defaultstate="collapsed">
     // Use the previous comparator and check the static methods of the Comparator interface.
     // </editor-fold>
-    
+
     /**
      * Write a Comparator that compares two people by age.
      * Try to write the comparator so as to avoid boxing of primitives.
@@ -129,7 +129,7 @@ public class B_Comparators {
         //BEGINREMOVE
         Comparator<Person> comparebyAge = Comparator.comparingInt(Person::getAge);
         //ENDREMOVE
-        
+
         assertTrue(comparebyAge.compare(michael, rod) < 0);
         assertTrue(comparebyAge.compare(paul, paul) == 0);
         assertTrue(comparebyAge.compare(mick, jermaine) > 0);
@@ -139,7 +139,7 @@ public class B_Comparators {
     // Look for static methods on the Comparator interface that
     // have primitive specializations.
     // </editor-fold>
-    
+
     /**
      * Write a lambda expression that compares two int values and returns an
      * int result that is less than, equal to, or greater than zero, like
@@ -155,7 +155,7 @@ public class B_Comparators {
         // Avoid the following as it is susceptible to overflow:
         // IntBinaryOperator intCompare = (a, b) -> a - b;
         //ENDREMOVE
-        
+
         assertTrue(intCompare.applyAsInt(0, 1) < 0);
         assertTrue(intCompare.applyAsInt(1, 1) == 0);
         assertTrue(intCompare.applyAsInt(2, 1) > 0);
@@ -178,7 +178,7 @@ public class B_Comparators {
         //BEGINREMOVE
         IntBinaryOperator intCompare = Integer::compare;
         //ENDREMOVE
-        
+
         assertTrue(intCompare.applyAsInt(0, 1) < 0);
         assertTrue(intCompare.applyAsInt(1, 1) == 0);
         assertTrue(intCompare.applyAsInt(2, 1) > 0);
@@ -193,7 +193,7 @@ public class B_Comparators {
     interface DoubleToIntBiFunction {
         int applyAsInt(double a, double b);
     }
-    
+
     /**
      * Write a method reference that compares two double values and returns an
      * int result that is less than, equal to, or greater than zero, like
@@ -208,7 +208,7 @@ public class B_Comparators {
         //BEGINREMOVE
         DoubleToIntBiFunction doubleCompare = Double::compare;
         //ENDREMOVE
-        
+
         assertTrue(doubleCompare.applyAsInt(0.0, 1.0) < 0);
         assertTrue(doubleCompare.applyAsInt(1.0, 1.0) == 0);
         assertTrue(doubleCompare.applyAsInt(2.0, 1.0) > 0);

LambdaLab/test/solutions/Exercises.java

@@ -587,11 +587,11 @@ public class Exercises {
                 "substantial"),
             result);
     }
-    // Hint:
+    // Hint 1:
     // <editor-fold defaultstate="collapsed">
     // Use Stream.distinct().
     // </editor-fold>
-    // Hint:
+    // Hint 2:
     // <editor-fold defaultstate="collapsed">
     // Use Comparator.theComparing().
     // </editor-fold>