Scheduler instances should be or behave like singletons

- remove the Func0 factory signature for Scheduler creation.

Author: benjchristensen

rxjava-core/src/main/java/rx/plugins/RxJavaDefaultSchedulers.java

@@ -16,7 +16,6 @@
 package rx.plugins;
 
 import rx.Scheduler;
-import rx.functions.Func0;
 
 /**
  * Define alternate Scheduler implementations to be returned by the `Schedulers` factory methods.
@@ -27,17 +26,23 @@
 public abstract class RxJavaDefaultSchedulers {
 
     /**
-     * Factory of Scheduler to return from {@link Schedulers.computation()} or null if default should be used.
+     * Scheduler to return from {@link Schedulers.computation()} or null if default should be used.
+     * 
+     * This instance should be or behave like a stateless singleton;
      */
-    public abstract Func0<Scheduler> getComputationSchedulerFactory();
+    public abstract Scheduler getComputationScheduler();
 
     /**
-     * Factory of Scheduler to return from {@link Schedulers.io()} or null if default should be used.
+     * Scheduler to return from {@link Schedulers.io()} or null if default should be used.
+     * 
+     * This instance should be or behave like a stateless singleton;
      */
-    public abstract Func0<Scheduler> getIOSchedulerFactory();
+    public abstract Scheduler getIOScheduler();
 
     /**
-     * Factory of Scheduler to return from {@link Schedulers.newThread()} or null if default should be used.
+     * Scheduler to return from {@link Schedulers.newThread()} or null if default should be used.
+     * 
+     * This instance should be or behave like a stateless singleton;
      */
-    public abstract Func0<Scheduler> getNewThreadSchedulerFactory();
+    public abstract Scheduler getNewThreadScheduler();
 }

rxjava-core/src/main/java/rx/plugins/RxJavaDefaultSchedulersDefault.java

@@ -16,7 +16,6 @@
 package rx.plugins;
 
 import rx.Scheduler;
-import rx.functions.Func0;
 
 /**
  * Default implementation of {@link RxJavaErrorHandler} that does nothing.
@@ -27,20 +26,23 @@ public class RxJavaDefaultSchedulersDefault extends RxJavaDefaultSchedulers {
 
     private static RxJavaDefaultSchedulersDefault INSTANCE = new RxJavaDefaultSchedulersDefault();
 
-    public Func0<Scheduler> getComputationSchedulerFactory() {
-        return null;
+    public static RxJavaDefaultSchedulers getInstance() {
+        return INSTANCE;
     }
 
-    public Func0<Scheduler> getIOSchedulerFactory() {
+    @Override
+    public Scheduler getComputationScheduler() {
         return null;
     }
 
-    public Func0<Scheduler> getNewThreadSchedulerFactory() {
+    @Override
+    public Scheduler getIOScheduler() {
         return null;
     }
 
-    public static RxJavaDefaultSchedulers getInstance() {
-        return INSTANCE;
+    @Override
+    public Scheduler getNewThreadScheduler() {
+        return null;
     }
 
 }

rxjava-core/src/main/java/rx/schedulers/Schedulers.java

@@ -23,61 +23,39 @@
 import java.util.concurrent.atomic.AtomicLong;
 
 import rx.Scheduler;
-import rx.functions.Func0;
 import rx.plugins.RxJavaPlugins;
 
 /**
  * Static factory methods for creating Schedulers.
  */
 public class Schedulers {
 
-    private final Func0<Scheduler> computationScheduler;
-    private final Func0<Scheduler> ioScheduler;
-    private final Func0<Scheduler> newThreadScheduler;
+    private final Scheduler computationScheduler;
+    private final Scheduler ioScheduler;
+    private final Scheduler newThreadScheduler;
 
     private static final Schedulers INSTANCE = new Schedulers();
 
     private Schedulers() {
-        Func0<Scheduler> c = RxJavaPlugins.getInstance().getDefaultSchedulers().getComputationSchedulerFactory();
+        Scheduler c = RxJavaPlugins.getInstance().getDefaultSchedulers().getComputationScheduler();
         if (c != null) {
             computationScheduler = c;
         } else {
-            computationScheduler = new Func0<Scheduler>() {
-
-                @Override
-                public Scheduler call() {
-                    return executor(createComputationExecutor());
-                }
-
-            };
+            computationScheduler = executor(createComputationExecutor());
         }
 
-        Func0<Scheduler> io = RxJavaPlugins.getInstance().getDefaultSchedulers().getIOSchedulerFactory();
+        Scheduler io = RxJavaPlugins.getInstance().getDefaultSchedulers().getIOScheduler();
         if (io != null) {
             ioScheduler = io;
         } else {
-            ioScheduler = new Func0<Scheduler>() {
-
-                @Override
-                public Scheduler call() {
-                    return executor(createIOExecutor());
-                }
-
-            };
+            ioScheduler = executor(createIOExecutor());
         }
 
-        Func0<Scheduler> nt = RxJavaPlugins.getInstance().getDefaultSchedulers().getNewThreadSchedulerFactory();
+        Scheduler nt = RxJavaPlugins.getInstance().getDefaultSchedulers().getNewThreadScheduler();
         if (nt != null) {
             newThreadScheduler = nt;
         } else {
-            newThreadScheduler = new Func0<Scheduler>() {
-
-                @Override
-                public Scheduler call() {
-                    return NewThreadScheduler.instance();
-                }
-
-            };
+            newThreadScheduler = NewThreadScheduler.instance();
         }
 
     }
@@ -117,7 +95,7 @@ public static Scheduler trampoline() {
      * @return {@link NewThreadScheduler} instance
      */
     public static Scheduler newThread() {
-        return INSTANCE.newThreadScheduler.call();
+        return INSTANCE.newThreadScheduler;
     }
 
     /**
@@ -167,7 +145,7 @@ public static Scheduler threadPoolForComputation() {
      * @return {@link Scheduler} for computation-bound work.
      */
     public static Scheduler computation() {
-        return INSTANCE.computationScheduler.call();
+        return INSTANCE.computationScheduler;
     }
 
     /**
@@ -199,7 +177,7 @@ public static Scheduler threadPoolForIO() {
      * @return {@link ExecutorScheduler} for IO-bound work.
      */
     public static Scheduler io() {
-        return INSTANCE.ioScheduler.call();
+        return INSTANCE.ioScheduler;
     }
 
     private static ScheduledExecutorService createComputationExecutor() {