Improvements during editing

collectiontopics/CanonicalMapping.java

@@ -15,7 +15,7 @@ class Element {
   @Override
   public boolean equals(Object r) {
     return r instanceof Element &&
-      ident.equals(((Element)r).ident);
+      Objects.equals(ident, ((Element)r).ident);
   }
   @Override
   protected void finalize() {

collectiontopics/ComposedEquality.java

@@ -0,0 +1,65 @@
+// collectiontopics/ComposedEquality.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+import java.util.*;
+
+class Part {
+  String ss;
+  double dd;
+  public Part(String ss, double dd) {
+    this.ss = ss;
+    this.dd = dd;
+  }
+  @Override
+  public boolean equals(Object rval) {
+    return rval instanceof Part &&
+      Objects.equals(ss, ((Part)rval).ss) &&
+      Objects.equals(dd, ((Part)rval).dd);
+  }
+}
+
+public class ComposedEquality extends SuccinctEquality {
+  Part part;
+  public ComposedEquality(int i, String s, double d) {
+    super(i, s, d);
+    part = new Part(s, d);
+    System.out.println("made 'ComposedEquality'");
+  }
+  @Override
+  public boolean equals(Object rval) {
+    return rval instanceof ComposedEquality &&
+      super.equals(rval) &&
+      Objects.equals(part, ((ComposedEquality)rval).part);
+  }
+  public static void main(String[] args) {
+    Equality.testAll( (i, s, d) ->
+      new ComposedEquality(i, s, d));
+  }
+}
+/* Output:
+made 'Equality'
+made 'SuccinctEquality'
+made 'ComposedEquality'
+made 'Equality'
+made 'SuccinctEquality'
+made 'ComposedEquality'
+made 'Equality'
+made 'SuccinctEquality'
+made 'ComposedEquality'
+-- Testing null --
+null instanceof Equality: false
+Expected false, got false
+-- Testing same object --
+same object instanceof Equality: true
+Expected true, got true
+-- Testing different type --
+different type instanceof Equality: false
+Expected false, got false
+-- Testing same values --
+same values instanceof Equality: true
+Expected true, got true
+-- Testing different values --
+different values instanceof Equality: true
+Expected false, got false
+*/

collectiontopics/CountedString.java

@@ -37,8 +37,8 @@ public class CountedString {
   @Override
   public boolean equals(Object o) {
     return o instanceof CountedString &&
-      s.equals(((CountedString)o).s) &&
+      Objects.equals(s, ((CountedString)o).s) &&
-      id == ((CountedString)o).id;
+      Objects.equals(id, ((CountedString)o).id);
   }
   public static void main(String[] args) {
     Map<CountedString,Integer> map =

collectiontopics/Equality.java

@@ -0,0 +1,76 @@
+// collectiontopics/Equality.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+import java.util.*;
+
+public class Equality {
+  protected int i;
+  protected String s;
+  protected double d;
+  public Equality(int i, String s, double d) {
+    this.i = i;
+    this.s = s;
+    this.d = d;
+    System.out.println("made 'Equality'");
+  }
+  @Override
+  public boolean equals(Object rval) {
+    if(rval == null)
+      return false;
+    if(rval == this)
+      return true;
+    if(!(rval instanceof Equality))
+      return false;
+    Equality other = (Equality)rval;
+    if(!Objects.equals(i, other.i))
+      return false;
+    if(!Objects.equals(s, other.s))
+      return false;
+    if(!Objects.equals(d, other.d))
+      return false;
+    return true;
+  }
+  public void
+  test(String descr, String expected, Object rval) {
+    System.out.format("-- Testing %s --%n" +
+      "%s instanceof Equality: %s%n" +
+      "Expected %s, got %s%n",
+      descr, descr, rval instanceof Equality,
+      expected, equals(rval));
+  }
+  public static void testAll(EqualityFactory eqf) {
+    Equality
+      e = eqf.make(1, "Monty", 3.14),
+      eq = eqf.make(1, "Monty", 3.14),
+      neq = eqf.make(99, "Bob", 1.618);
+    e.test("null", "false", null);
+    e.test("same object", "true", e);
+    e.test("different type", "false", new Integer(99));
+    e.test("same values", "true", eq);
+    e.test("different values", "false", neq);
+  }
+  public static void main(String[] args) {
+    testAll( (i, s, d) -> new Equality(i, s, d));
+  }
+}
+/* Output:
+made 'Equality'
+made 'Equality'
+made 'Equality'
+-- Testing null --
+null instanceof Equality: false
+Expected false, got false
+-- Testing same object --
+same object instanceof Equality: true
+Expected true, got true
+-- Testing different type --
+different type instanceof Equality: false
+Expected false, got false
+-- Testing same values --
+same values instanceof Equality: true
+Expected true, got true
+-- Testing different values --
+different values instanceof Equality: true
+Expected false, got false
+*/

collectiontopics/EqualityFactory.java

@@ -0,0 +1,9 @@
+// collectiontopics/EqualityFactory.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+import java.util.*;
+
+interface EqualityFactory {
+  Equality make(int i, String s, double d);
+}

collectiontopics/Groundhog2.java

@@ -4,6 +4,7 @@
 // Visit http://OnJava8.com for more book information.
 // A class that's used as a key in a HashMap
 // must override hashCode() and equals()
+import java.util.*;
 
 public class Groundhog2 extends Groundhog {
   public Groundhog2(int n) { super(n); }
@@ -12,6 +13,7 @@ public class Groundhog2 extends Groundhog {
   @Override
   public boolean equals(Object o) {
     return o instanceof Groundhog2 &&
-      (number == ((Groundhog2)o).number);
+      Objects.equals(
+        number, ((Groundhog2)o).number);
   }
 }

collectiontopics/MapEntry.java

@@ -34,10 +34,10 @@ public class MapEntry<K, V> implements Map.Entry<K, V> {
     MapEntry<K, V> me = (MapEntry<K, V>)o;
     return
       (key == null ? me.getKey() == null :
-       key.equals(me.getKey()))
+        key.equals(me.getKey()))
        &&
       (value == null ? me.getValue() == null :
-       value.equals(me.getValue()));
+        value.equals(me.getValue()));
   }
   @Override
   public String toString() { return key + "=" + value; }

collectiontopics/SuccinctEquality.java

@@ -0,0 +1,46 @@
+// collectiontopics/SuccinctEquality.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+import java.util.*;
+
+public class SuccinctEquality extends Equality {
+  public SuccinctEquality(int i, String s, double d) {
+    super(i, s, d);
+    System.out.println("made 'SuccinctEquality'");
+  }
+  @Override
+  public boolean equals(Object rval) {
+    return rval instanceof SuccinctEquality &&
+      Objects.equals(i, ((SuccinctEquality)rval).i) &&
+      Objects.equals(s, ((SuccinctEquality)rval).s) &&
+      Objects.equals(d, ((SuccinctEquality)rval).d);
+  }
+  public static void main(String[] args) {
+    Equality.testAll( (i, s, d) ->
+      new SuccinctEquality(i, s, d));
+  }
+}
+/* Output:
+made 'Equality'
+made 'SuccinctEquality'
+made 'Equality'
+made 'SuccinctEquality'
+made 'Equality'
+made 'SuccinctEquality'
+-- Testing null --
+null instanceof Equality: false
+Expected false, got false
+-- Testing same object --
+same object instanceof Equality: true
+Expected true, got true
+-- Testing different type --
+different type instanceof Equality: false
+Expected false, got false
+-- Testing same values --
+same values instanceof Equality: true
+Expected true, got true
+-- Testing different values --
+different values instanceof Equality: true
+Expected false, got false
+*/

collectiontopics/TypesForSets.java

@@ -12,7 +12,6 @@ class SetType {
   public SetType(int n) { i = n; }
   @Override
   public boolean equals(Object o) {
-    if (o == this) return true;
     return o instanceof SetType &&
       Objects.equals(i, ((SetType)o).i);
   }

collectiontopics/Unsupported.java

@@ -6,37 +6,28 @@
 import java.util.*;
 
 public class Unsupported {
+  static void check(String description, Runnable tst) {
+    try {
+      tst.run();
+    } catch(Exception e) {
+      System.out.println(description + "(): " + e);
+    }
+  }
   static void test(String msg, List<String> list) {
     System.out.println("--- " + msg + " ---");
     Collection<String> c = list;
     Collection<String> subList = list.subList(1,8);
     // Copy of the sublist:
     Collection<String> c2 = new ArrayList<>(subList);
-    try { c.retainAll(c2); } catch(Exception e) {
+    check("retainAll", () -> c.retainAll(c2));
-      System.out.println("retainAll(): " + e);
+    check("removeAll", () -> c.removeAll(c2));
-    }
+    check("clear", () -> c.clear());
-    try { c.removeAll(c2); } catch(Exception e) {
+    check("add", () -> c.add("X"));
-      System.out.println("removeAll(): " + e);
+    check("addAll", () -> c.addAll(c2));
-    }
+    check("remove", () -> c.remove("C"));
-    try { c.clear(); } catch(Exception e) {
-      System.out.println("clear(): " + e);
-    }
-    try { c.add("X"); } catch(Exception e) {
-      System.out.println("add(): " + e);
-    }
-    try { c.addAll(c2); } catch(Exception e) {
-      System.out.println("addAll(): " + e);
-    }
-    try { c.remove("C"); } catch(Exception e) {
-      System.out.println("remove(): " + e);
-    }
     // The List.set() method modifies the value but
     // doesn't change the size of the data structure:
-    try {
+    check("List.set", () -> list.set(0, "X"));
-      list.set(0, "X");
-    } catch(Exception e) {
-      System.out.println("List.set(): " + e);
-    }
   }
   public static void main(String[] args) {
     List<String> list =

generics/Holder.java

@@ -12,7 +12,6 @@ public class Holder<T> {
   public T get() { return value; }
   @Override
   public boolean equals(Object o) {
-    if (o == this) return true;
     return o instanceof Holder &&
       Objects.equals(value, ((Holder)o).value);
   }

onjava/CountMap.java

@@ -6,6 +6,7 @@
 // {java onjava.CountMap}
 package onjava;
 import java.util.*;
+import java.util.stream.*;
 
 public class CountMap
 extends AbstractMap<Integer,String> {
@@ -31,7 +32,8 @@ extends AbstractMap<Integer,String> {
     Entry(int index) { this.index = index; }
     @Override
     public boolean equals(Object o) {
-      return Integer.valueOf(index).equals(o);
+      return o instanceof Entry &&
+        Objects.equals(index, ((Entry)o).index);
     }
     @Override
     public Integer getKey() { return index; }
@@ -49,11 +51,10 @@ extends AbstractMap<Integer,String> {
   @Override
   public Set<Map.Entry<Integer,String>> entrySet() {
     // LinkedHashSet retains initialization order:
-    Set<Map.Entry<Integer,String>> entries =
+    return IntStream.range(0, size)
-      new LinkedHashSet<>();
+      .mapToObj(Entry::new)
-    for(int i = 0; i < size; i++)
+      .collect(
-      entries.add(new Entry(i));
+        Collectors.toCollection(LinkedHashSet::new));
-    return entries;
   }
   public static void main(String[] args) {
     CountMap cm = new CountMap(60);

onjava/Countries.java

@@ -220,7 +220,12 @@ public class Countries {
       Entry(int index) { this.index = index; }
       @Override
       public boolean equals(Object o) {
-        return DATA[index][0].equals(o);
+        return o instanceof FlyweightMap &&
+          Objects.equals(DATA[index][0], o);
+      }
+      @Override
+      public int hashCode() {
+        return DATA[index][0].hashCode();
       }
       @Override
       public String getKey() { return DATA[index][0]; }
@@ -230,10 +235,6 @@ public class Countries {
       public String setValue(String value) {
         throw new UnsupportedOperationException();
       }
-      @Override
-      public int hashCode() {
-        return DATA[index][0].hashCode();
-      }
     }
     // Implement size() & iterator() for AbstractSet:
     static class EntrySet

patterns/ShapeFactory1.java

@@ -0,0 +1,47 @@
+// patterns/ShapeFactory1.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+// A simple static factory method
+import java.util.*;
+import java.util.stream.*;
+import patterns.shapes.*;
+
+class StaticFactory {
+  static Shape create(String type) {
+    switch(type) {
+      case "Circle": return new Circle();
+      case "Square": return new Square();
+      case "Triangle": return new Triangle();
+      default:
+        throw new BadShapeCreation(type);
+    }
+  }
+}
+
+public class ShapeFactory1 {
+  public static void main(String[] args) {
+    Stream.of("Circle", "Square", "Triangle",
+      "Square", "Circle", "Circle", "Triangle")
+      .map(StaticFactory::create)
+      .peek(Shape::draw)
+      .peek(Shape::erase)
+      .count(); // Terminal operation
+  }
+}
+/* Output:
+Circle[0] draw
+Circle[0] erase
+Square[1] draw
+Square[1] erase
+Triangle[2] draw
+Triangle[2] erase
+Square[3] draw
+Square[3] erase
+Circle[4] draw
+Circle[4] erase
+Circle[5] draw
+Circle[5] erase
+Triangle[6] draw
+Triangle[6] erase
+*/

patterns/ShapeFactory2.java

@@ -2,87 +2,60 @@
 // (c)2017 MindView LLC: see Copyright.txt
 // We make no guarantees that this code is fit for any purpose.
 // Visit http://OnJava8.com for more book information.
-// Polymorphic factory methods
 import java.util.*;
-import java.util.function.*;
+import java.lang.reflect.*;
 import java.util.stream.*;
+import patterns.shapes.*;
 
-class BadShapeCreation extends RuntimeException {
+class DynamicFactory {
-  BadShapeCreation(String msg) {
+  static Map<String, Constructor> factories =
-    super(msg);
-  }
-}
-
-interface Shape {
-  void draw();
-  void erase();
-}
-
-abstract class ShapeFactory {
-  static Map<String, Supplier<Shape>> factories =
     new HashMap<>();
-  static Shape createShape(String id) {
+  static Constructor load(String id) {
-    if(!factories.containsKey(id)) {
+    System.out.println("loading " + id);
-      try {
+    try {
-        Class.forName(id); // Load dynamically
+      return Class.forName("patterns.shapes." + id)
-      } catch(ClassNotFoundException e) {
+        .getConstructor();
-        throw new BadShapeCreation(id);
+    } catch(Exception e) {
-      }
+      throw new BadShapeCreation(id);
-      // See if it was put in:
-      if(!factories.containsKey(id))
-        throw new BadShapeCreation(id);
     }
-    return factories.get(id).get();
   }
-}
+  static Shape create(String id) {
-
+    try {
-final class Circle implements Shape {
+      return (Shape)factories
-  private Circle() {}
+        .computeIfAbsent(id, DynamicFactory::load)
-  public void draw() {
+        .newInstance();
-    System.out.println("Circle.draw");
+    } catch(Exception e) {
-  }
+      throw new BadShapeCreation(id);
-  public void erase() {
+    }
-    System.out.println("Circle.erase");
-  }
-  static {
-    ShapeFactory.factories.put("Circle", Circle::new);
-  }
-}
-
-final class Square implements Shape {
-  private Square() {}
-  public void draw() {
-    System.out.println("Square.draw");
-  }
-  public void erase() {
-    System.out.println("Square.erase");
-  }
-  static {
-    ShapeFactory.factories.put("Square", Square::new);
   }
 }
 
 public class ShapeFactory2 {
   public static void main(String[] args) {
-    List<Shape> shapes = Stream.of("Circle", "Square",
+    Stream.of("Circle", "Square", "Triangle",
-      "Square", "Circle", "Circle", "Square")
+      "Square", "Circle", "Circle", "Triangle")
-      .map(ShapeFactory::createShape)
+      .map(DynamicFactory::create)
-      .collect(Collectors.toList());
+      .peek(Shape::draw)
-    shapes.forEach(Shape::draw);
+      .peek(Shape::erase)
-    shapes.forEach(Shape::erase);
+      .count();
   }
 }
 /* Output:
-Circle.draw
+loading Circle
-Square.draw
+Circle[0] draw
-Square.draw
+Circle[0] erase
-Circle.draw
+loading Square
-Circle.draw
+Square[1] draw
-Square.draw
+Square[1] erase
-Circle.erase
+loading Triangle
-Square.erase
+Triangle[2] draw
-Square.erase
+Triangle[2] erase
-Circle.erase
+Square[3] draw
-Circle.erase
+Square[3] erase
-Square.erase
+Circle[4] draw
+Circle[4] erase
+Circle[5] draw
+Circle[5] erase
+Triangle[6] draw
+Triangle[6] erase
 */

patterns/ShapeFactory3.java

@@ -0,0 +1,53 @@
+// patterns/ShapeFactory3.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+// Polymorphic factory methods
+import java.util.*;
+import java.util.function.*;
+import java.util.stream.*;
+import patterns.shapes.*;
+
+interface PolymorphicFactory {
+  Shape create();
+}
+
+class RandomShapes implements Supplier<Shape> {
+  private final PolymorphicFactory[] factories;
+  private Random rand = new Random(42);
+  public
+  RandomShapes(PolymorphicFactory... factories) {
+    this.factories = factories;
+  }
+  public Shape get() {
+    return factories[
+      rand.nextInt(factories.length)].create();
+  }
+}
+
+public class ShapeFactory3 {
+  public static void main(String[] args) {
+    RandomShapes rs = new RandomShapes(
+      Circle::new, Square::new, Triangle::new
+    );
+    Stream.generate(rs)
+      .limit(6)
+      .peek(Shape::draw)
+      .peek(Shape::erase)
+      .count();
+  }
+}
+/* Output:
+Triangle[0] draw
+Triangle[0] erase
+Circle[1] draw
+Circle[1] erase
+Circle[2] draw
+Circle[2] erase
+Triangle[3] draw
+Triangle[3] erase
+Circle[4] draw
+Circle[4] erase
+Square[5] draw
+Square[5] erase
+*/

patterns/abstractfactory/GameEnvironment.java

@@ -1,10 +1,10 @@
-// patterns/absfactory/GameEnvironment.java
+// patterns/abstractfactory/GameEnvironment.java
 // (c)2017 MindView LLC: see Copyright.txt
 // We make no guarantees that this code is fit for any purpose.
 // Visit http://OnJava8.com for more book information.
 // An example of the Abstract Factory pattern
-// {java patterns.absfactory.GameEnvironment}
+// {java patterns.abstractfactory.GameEnvironment}
-package patterns.absfactory;
+package patterns.abstractfactory;
 import java.util.function.*;
 
 interface Obstacle {

patterns/factory/ShapeFactory1.java

@@ -1,79 +0,0 @@
-// patterns/factory/ShapeFactory1.java
-// (c)2017 MindView LLC: see Copyright.txt
-// We make no guarantees that this code is fit for any purpose.
-// Visit http://OnJava8.com for more book information.
-// A simple static factory method
-// {java patterns.factory.ShapeFactory1}
-package patterns.factory;
-import java.util.*;
-import java.util.stream.*;
-
-class BadShapeCreation extends RuntimeException {
-  BadShapeCreation(String msg) {
-    super(msg);
-  }
-}
-
-abstract class Shape {
-  public abstract void draw();
-  public abstract void erase();
-  static Shape factory(String type) {
-    switch(type) {
-      case "Circle": return new Circle();
-      case "Square": return new Square();
-      default:
-        throw new BadShapeCreation(type);
-    }
-  }
-}
-
-class Circle extends Shape {
-  Circle() {} // Friendly constructor
-  @Override
-  public void draw() {
-    System.out.println("Circle.draw");
-  }
-  @Override
-  public void erase() {
-    System.out.println("Circle.erase");
-  }
-}
-
-class Square extends Shape {
-  Square() {} // Friendly constructor
-  @Override
-  public void draw() {
-    System.out.println("Square.draw");
-  }
-  @Override
-  public void erase() {
-    System.out.println("Square.erase");
-  }
-}
-
-public class ShapeFactory1 {
-  public static void main(String[] args) {
-    List<Shape> shapes = Stream.of(
-      "Circle", "Square",
-      "Square", "Circle",
-      "Circle", "Square")
-      .map(Shape::factory)
-      .collect(Collectors.toList());
-    shapes.forEach(Shape::draw);
-    shapes.forEach(Shape::erase);
-  }
-}
-/* Output:
-Circle.draw
-Square.draw
-Square.draw
-Circle.draw
-Circle.draw
-Square.draw
-Circle.erase
-Square.erase
-Square.erase
-Circle.erase
-Circle.erase
-Square.erase
-*/

patterns/recyclea/RecycleA.java

@@ -66,7 +66,8 @@ class TrashFactory {
     Arrays.asList(
       Aluminum::new, Paper::new, Glass::new);
   static final int SZ = ttypes.size();
-  private static SplittableRandom rand = new SplittableRandom(47);
+  private static SplittableRandom rand =
+    new SplittableRandom(47);
   public static Trash newTrash() {
     return ttypes
       .get(rand.nextInt(SZ))

patterns/shapes/BadShapeCreation.java

@@ -0,0 +1,12 @@
+// patterns/shapes/BadShapeCreation.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+package patterns.shapes;
+
+public class BadShapeCreation
+extends RuntimeException {
+  public BadShapeCreation(String msg) {
+    super(msg);
+  }
+}

patterns/shapes/Circle.java

@@ -0,0 +1,7 @@
+// patterns/shapes/Circle.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+package patterns.shapes;
+
+public class Circle extends Shape {}

patterns/shapes/Shape.java

@@ -0,0 +1,21 @@
+// patterns/shapes/Shape.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+package patterns.shapes;
+
+public class Shape {
+  private static int counter = 0;
+  private int id = counter++;
+  @Override
+  public String toString() {
+    return
+      getClass().getSimpleName() + "[" + id + "]";
+  }
+  public void draw() {
+    System.out.println(this + " draw");
+  }
+  public void erase() {
+    System.out.println(this + " erase");
+  }
+}

patterns/shapes/Square.java

@@ -0,0 +1,7 @@
+// patterns/shapes/Square.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+package patterns.shapes;
+
+public class Square extends Shape {}

patterns/shapes/Triangle.java

@@ -0,0 +1,7 @@
+// patterns/shapes/Triangle.java
+// (c)2017 MindView LLC: see Copyright.txt
+// We make no guarantees that this code is fit for any purpose.
+// Visit http://OnJava8.com for more book information.
+package patterns.shapes;
+
+public class Triangle extends Shape {}

typeinfo/pets/Individual.java

@@ -3,6 +3,7 @@
 // We make no guarantees that this code is fit for any purpose.
 // Visit http://OnJava8.com for more book information.
 package typeinfo.pets;
+import java.util.*;
 
 public class
 Individual implements Comparable<Individual> {
@@ -21,7 +22,7 @@ Individual implements Comparable<Individual> {
   @Override
   public boolean equals(Object o) {
     return o instanceof Individual &&
-      id == ((Individual)o).id;
+      Objects.equals(id, ((Individual)o).id);
   }
   @Override
   public int hashCode() {