Upcast ConcurrentHashMap to Map to avoid compatibility issue (#4654)

* Upcast ConcurrentHashMap to Map to avoid compatibility issue

Resovles #4653

See http://stackoverflow.com/a/32955708/61158

* Fix imports, remove now-unnecessary animalsniffer suppression

Author: ZacSweers

src/main/java/io/reactivex/internal/schedulers/SchedulerPoolFactory.java

@@ -20,7 +20,6 @@
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicReference;
 
-import io.reactivex.internal.util.SuppressAnimalSniffer;
 import io.reactivex.plugins.RxJavaPlugins;
 
 /**
@@ -46,7 +45,9 @@ public enum SchedulerPoolFactory {
     static final AtomicReference<ScheduledExecutorService> PURGE_THREAD =
             new AtomicReference<ScheduledExecutorService>();
 
-    static final ConcurrentHashMap<ScheduledThreadPoolExecutor, Object> POOLS =
+    // Upcast to the Map interface here to avoid 8.x compatibility issues.
+    // See http://stackoverflow.com/a/32955708/61158
+    static final Map<ScheduledThreadPoolExecutor, Object> POOLS =
             new ConcurrentHashMap<ScheduledThreadPoolExecutor, Object>();
 
     /**
@@ -63,10 +64,9 @@ public static void start() {
 
                 next.scheduleAtFixedRate(new Runnable() {
                     @Override
-                    @SuppressAnimalSniffer
                     public void run() {
                         try {
-                            for (ScheduledThreadPoolExecutor e : new ArrayList<ScheduledThreadPoolExecutor>(POOLS.keySet())) {  // CHM.keySet returns KeySetView in Java 8+; false positive here
+                            for (ScheduledThreadPoolExecutor e : new ArrayList<ScheduledThreadPoolExecutor>(POOLS.keySet())) {
                                 if (e.isShutdown()) {
                                     POOLS.remove(e);
                                 } else {