Some cleanups during rewrite

lowlevel/AttemptLocking.java

@@ -6,6 +6,7 @@
 // to give up on trying to acquire a lock
 import java.util.concurrent.*;
 import java.util.concurrent.locks.*;
+import onjava.Nap;
 
 public class AttemptLocking {
   private ReentrantLock lock = new ReentrantLock();
@@ -46,7 +47,7 @@ public class AttemptLocking {
         System.out.println("acquired");
       }
     }.start();
-    Thread.yield(); // Give the 2nd task a chance
+    new Nap(10);  // Give the 2nd task a chance
     al.untimed(); // False -- lock grabbed by task
     al.timed();   // False -- lock grabbed by task
   }

lowlevel/CriticalSection.java

@@ -2,12 +2,9 @@
 // (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.
-// (Behavior may have changed in Java 8)
 // Synchronizing blocks instead of entire methods. Also
 // demonstrates protection of a non-thread-safe class
 // with a thread-safe one.
-// {java lowlevel.CriticalSection}
-package lowlevel;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.*;
 import java.util.*;

lowlevel/ExplicitCriticalSection.java

@@ -1,79 +0,0 @@
-// lowlevel/ExplicitCriticalSection.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.
-// {ThrowsException} on a multiprocessor machine
-// Using explicit Lock objects to create critical sections
-// {java lowlevel.ExplicitCriticalSection}
-package lowlevel;
-import java.util.concurrent.locks.*;
-
-// Synchronize the entire method:
-class ExplicitPairManager1 extends PairManager {
-  private Lock lock = new ReentrantLock();
-  @Override
-  public void increment() {
-    lock.lock();
-    try {
-      p.incrementX();
-      p.incrementY();
-      store(getPair());
-    } finally {
-      lock.unlock();
-    }
-  }
-}
-
-// Use a critical section:
-class ExplicitPairManager2 extends PairManager {
-  private Lock lock = new ReentrantLock();
-  @Override
-  public void increment() {
-    Pair temp;
-    lock.lock();
-    try {
-      p.incrementX();
-      p.incrementY();
-      temp = getPair();
-    } finally {
-      lock.unlock();
-    }
-    store(temp);
-  }
-}
-
-public class ExplicitCriticalSection {
-  public static void
-  main(String[] args) throws Exception {
-    PairManager
-      pman1 = new ExplicitPairManager1(),
-      pman2 = new ExplicitPairManager2();
-    CriticalSection.testApproaches(pman1, pman2);
-  }
-}
-/* Output:
-pm1: Pair: x: 10, y: 10 checkCounter = 1713716
-pm2: Pair: x: 10, y: 10 checkCounter = 1717747
-___[ Error Output ]___
-Exception in thread "pool-1-thread-4" Exception in thread
-"pool-1-thread-3" threads.Pair$PairValuesNotEqualException:
-Pair values not equal: x: 2, y: 1
-        at threads.Pair.checkState(CriticalSection.java:37)
-        at
-threads.PairChecker.run(CriticalSection.java:111)
-        at java.util.concurrent.ThreadPoolExecutor.runWorke
-r(ThreadPoolExecutor.java:1142)
-        at java.util.concurrent.ThreadPoolExecutor$Worker.r
-un(ThreadPoolExecutor.java:617)
-        at java.lang.Thread.run(Thread.java:745)
-threads.Pair$PairValuesNotEqualException: Pair values not
-equal: x: 2, y: 1
-        at threads.Pair.checkState(CriticalSection.java:37)
-        at
-threads.PairChecker.run(CriticalSection.java:111)
-        at java.util.concurrent.ThreadPoolExecutor.runWorke
-r(ThreadPoolExecutor.java:1142)
-        at java.util.concurrent.ThreadPoolExecutor$Worker.r
-un(ThreadPoolExecutor.java:617)
-        at java.lang.Thread.run(Thread.java:745)
-*/

lowlevel/MutexEvenProducer.java

@@ -5,6 +5,7 @@
 // Preventing thread collisions with mutexes
 // {IgnoreOutput} // No output validation
 import java.util.concurrent.locks.*;
+import onjava.Nap;
 
 public class MutexEvenProducer extends IntGenerator {
   private int currentEvenValue = 0;
@@ -14,7 +15,7 @@ public class MutexEvenProducer extends IntGenerator {
     lock.lock();
     try {
       ++currentEvenValue;
-      Thread.yield(); // Cause failure faster
+      new Nap(10); // Cause failure faster
       ++currentEvenValue;
       return currentEvenValue;
     } finally {

lowlevel/PriorityBlockingQueueDemo.java

@@ -73,7 +73,7 @@ class PrioritizedTaskProducer implements Runnable {
     // Fill it up fast with random priorities:
     for(int i = 0; i < 20; i++) {
       queue.add(new PrioritizedTask(rand.nextInt(10)));
-      Thread.yield();
+      new Nap(10);
     }
     // Trickle in highest-priority jobs:
     for(int i = 0; i < 10; i++) {

lowlevel/SyncObject.java

@@ -3,20 +3,21 @@
 // We make no guarantees that this code is fit for any purpose.
 // Visit http://OnJava8.com for more book information.
 // Synchronizing on another object
+import onjava.Nap;
 
 class DualSynch {
   private Object syncObject = new Object();
   public synchronized void f() {
     for(int i = 0; i < 5; i++) {
       System.out.println("f()");
-      Thread.yield();
+      new Nap(10);
     }
   }
   public void g() {
     synchronized(syncObject) {
       for(int i = 0; i < 5; i++) {
         System.out.println("g()");
-        Thread.yield();
+        new Nap(10);
       }
     }
   }