Code review/streamification

references/AddingClone.java

@@ -5,6 +5,7 @@
 // You must go through a few gyrations
 // to add cloning to your own class
 import java.util.*;
+import java.util.stream.*;
 
 class Int2 implements Cloneable {
   private int i;
@@ -41,18 +42,18 @@ public class AddingClone {
     // Anything inherited is also cloneable:
     Int3 x3 = new Int3(7);
     x3 = (Int3)x3.clone();
-    ArrayList<Int2> v = new ArrayList<>();
-    for(int i = 0; i < 10; i++ )
-      v.add(new Int2(i));
+    ArrayList<Int2> v = IntStream.range(0, 10)
+      .mapToObj(Int2::new)
+      .collect(Collectors
+        .toCollection(ArrayList::new));
     System.out.println("v: " + v);
     ArrayList<Int2> v2 =
       (ArrayList<Int2>)v.clone();
     // Now clone each element:
-    for(int i = 0; i < v.size(); i++)
-      v2.set(i, v2.get(i).clone());
+    IntStream.range(0, v.size())
+      .forEach(i -> v2.set(i, v.get(i).clone()));
     // Increment all v2's elements:
-    for(Int2 i2 : v2)
-      i2.increment();
+    v2.forEach(Int2::increment);
     System.out.println("v2: " + v2);
     // See if it changed v's elements:
     System.out.println("v: " + v);

references/CloneArrayList.java

@@ -5,6 +5,7 @@
 // The clone() operation works for only a few
 // items in the standard Java library
 import java.util.*;
+import java.util.stream.*;
 
 class Int {
   private int i;
@@ -18,15 +19,15 @@ class Int {
 
 public class CloneArrayList {
   public static void main(String[] args) {
-    ArrayList<Int> v = new ArrayList<>();
-    for(int i = 0; i < 10; i++)
-      v.add(new Int(i));
+    ArrayList<Int> v = IntStream.range(0, 10)
+      .mapToObj(Int::new)
+      .collect(Collectors
+        .toCollection(ArrayList::new));
     System.out.println("v: " + v);
     @SuppressWarnings("unchecked")
     ArrayList<Int> v2 = (ArrayList<Int>)v.clone();
     // Increment all v2's elements:
-    for(Int e : v2)
-      e.increment();
+    v2.forEach(Int::increment);
     // See if it changed v's elements:
     System.out.println("v: " + v);
   }

references/CopyConstructor.java

@@ -117,7 +117,7 @@ public class CopyConstructor {
       t.getClass().getName());
   }
   public static void slice(Fruit f) {
-    f = new Fruit(f); // Hmmm... will this work? (2)
+    f = new Fruit(f); // [2] Hmmm... will this work?
     System.out.println("In slice, f is a " +
       f.getClass().getName());
   }

references/ImmutableInteger.java

@@ -4,13 +4,18 @@
 // Visit http://OnJava8.com for more book information.
 // The Integer class cannot be changed
 import java.util.*;
+import java.util.stream.*;
 
 public class ImmutableInteger {
   public static void main(String[] args) {
-    List<Integer> v = new ArrayList<>();
-    for(int i = 0; i < 10; i++)
-      v.add(Integer.valueOf(i));
+    List<Integer> v = IntStream.range(0, 10)
+      .mapToObj(Integer::new)
+      .collect(Collectors.toList());
+    System.out.println(v);
     // But how do you change the int
     // inside the Integer?
   }
 }
+/* Output:
+[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+*/

references/MutableInteger.java

@@ -4,6 +4,7 @@
 // Visit http://OnJava8.com for more book information.
 // A changeable wrapper class
 import java.util.*;
+import java.util.stream.*;
 
 class IntValue {
   private int n;
@@ -19,12 +20,11 @@ class IntValue {
 
 public class MutableInteger {
   public static void main(String[] args) {
-    List<IntValue> v = new ArrayList<>();
-    for(int i = 0; i < 10; i++)
-      v.add(new IntValue(i));
+    List<IntValue> v = IntStream.range(0, 10)
+      .mapToObj(IntValue::new)
+      .collect(Collectors.toList());
     System.out.println(v);
-    for(int i = 0; i < v.size(); i++)
-      v.get(i).increment();
+    v.forEach(IntValue::increment);
     System.out.println(v);
   }
 }

references/SimplerMutableInteger.java

@@ -4,6 +4,7 @@
 // Visit http://OnJava8.com for more book information.
 // A trivial wrapper class
 import java.util.*;
+import java.util.stream.*;
 
 class IntValue2 {
   public int n;
@@ -12,16 +13,15 @@ class IntValue2 {
 
 public class SimplerMutableInteger {
   public static void main(String[] args) {
-    List<IntValue2> v = new ArrayList<>();
-    for(int i = 0; i < 10; i++)
-      v.add(new IntValue2(i));
-    for(IntValue2 i : v)
-      System.out.print(i.n + " ");
+    List<IntValue2> v = IntStream.range(0, 10)
+      .mapToObj(IntValue2::new)
+      .collect(Collectors.toList());
+    v.forEach(iv2 ->
+      System.out.print(iv2.n + " "));
     System.out.println();
-    for(int i = 0; i < v.size(); i++)
-      v.get(i).n = v.get(i).n + 1;
-    for(IntValue2 i : v)
-      System.out.print(i.n + " ");
+    v.forEach(iv2 -> iv2.n += 1);
+    v.forEach(iv2 ->
+      System.out.print(iv2.n + " "));
   }
 }
 /* Output:

references/Snake.java

@@ -40,7 +40,8 @@ public class Snake implements Cloneable {
     Snake s2 = s.clone();
     System.out.println("s2 = " + s2);
     s.increment();
-    System.out.println("after s.increment, s2 = " + s2);
+    System.out.println(
+      "after s.increment, s2 = " + s2);
   }
 }
 /* Output: