Added QuittingCompletable.java

concurrent/ParallelStreamPuzzle2.java

@@ -9,7 +9,7 @@ import java.util.concurrent.*;
 import java.nio.file.*;
 
 public class ParallelStreamPuzzle2 {
-  public static ConcurrentLinkedDeque<String> trace =
+  public static Deque<String> trace =
     new ConcurrentLinkedDeque<>();
   static class
   IntGenerator implements Supplier<Integer> {
@@ -20,8 +20,10 @@ public class ParallelStreamPuzzle2 {
       return current++;
     }
   }
-  public static void main(String[] args) throws Exception {
+  public static void
-    List<Integer> x = Stream.generate(new IntGenerator())
+  main(String[] args) throws Exception {
+    List<Integer> x =
+      Stream.generate(new IntGenerator())
         .limit(10)
         .parallel()
         .collect(Collectors.toList());

concurrent/QuittingCompletable.java

@@ -0,0 +1,35 @@
+// concurrent/QuittingCompletable.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.*;
+import java.util.stream.*;
+import java.util.concurrent.*;
+import onjava.Nap;
+
+public class QuittingCompletable {
+  public static void main(String[] args) {
+    List<QuittableTask> tasks =
+      IntStream.range(1, QuittingTasks.COUNT)
+        .mapToObj(QuittableTask::new)
+        .collect(Collectors.toList());
+    List<CompletableFuture<Void>> cfutures =
+      tasks.stream()
+        .map(CompletableFuture::runAsync)
+        .collect(Collectors.toList());
+    new Nap(1000);
+    tasks.forEach(QuittableTask::quit);
+    cfutures.forEach(CompletableFuture::join);
+  }
+}
+/* Output:
+125 148 115 127 120 118 106 140 77 119 97 80 143 17 92 147
+89 123 16 12 138 25 13 101 135 96 76 73 130 133 37 132 134
+149 137 122 29 49 60 40 142 131 53 1 98 145 126 65 5 64 82
+79 68 86 141 61 128 22 7 26 19 139 114 146 14 15 43 34 10
+75 87 90 31 47 38 62 18 63 41 42 144 66 23 6 4 91 70 83 102
+103 54 69 74 56 71 94 88 78 81 57 52 93 45 48 44 32 28 36
+33 104 105 112 109 100 117 24 108 21 116 20 9 85 8 84 72
+107 113 121 124 136 129 99 95 55 3 27 2 59 67 50 58 51 39
+30 35 46 110 111 11
+*/

concurrent/Summing.java

@@ -7,18 +7,18 @@ import java.util.function.*;
 import onjava.Timer;
 
 public class Summing {
-  static volatile long x;
+  static volatile long result;
   static void timeTest(String id, long checkValue,
     LongSupplier operation) {
     System.out.print(id + ": ");
     Timer timer = new Timer();
-    long result = operation.getAsLong();
+     // Prevent optimization:
+    result = operation.getAsLong();
     if(result == checkValue)
       System.out.println(timer.duration() + "ms");
     else
       System.out.format("result: %d%ncheckValue: %d%n",
         result, checkValue);
-    x = result; // Prevent optimization
   }
   public static final int SZ = 100_000_000;
   // This even works:
@@ -34,7 +34,7 @@ public class Summing {
     timeTest("Sum Iterated", CHECK, () ->
       LongStream.iterate(0, i -> i + 1)
         .limit(SZ+1).sum());
-    // Takes longer, runs out of memory above 1_000_000:
+    // Slower & runs out of memory above 1_000_000:
     // timeTest("Sum Iterated Parallel", CHECK, () ->
     //   LongStream.iterate(0, i -> i + 1)
     //     .parallel()

concurrent/Summing2.java

@@ -36,8 +36,8 @@ public class Summing2 {
 }
 /* Output:
 200000010000000
-Array Stream Sum: 22ms
+Array Stream Sum: 104ms
-Parallel: 21ms
+Parallel: 81ms
-Basic Sum: 16ms
+Basic Sum: 106ms
-parallelPrefix: 116ms
+parallelPrefix: 265ms
 */