introduced a default foreground task executor in ThreadPoolUtils which is used in AbstractSimpleLeaderboardImpl now

Change-Id: I46d039cb23e31bf7cf31598af3eb51b62b7a9520

java/com.sap.sse/src/com/sap/sse/util/ThreadPoolUtil.java

@@ -24,6 +24,24 @@ public interface ThreadPoolUtil {
      */
     ExecutorService getDefaultBackgroundTaskThreadPoolExecutor();
     
+    /**
+     * Returns a central, default thread pool executor that can be used to schedule foreground tasks. Using this
+     * centralized copy ensures that when several application modules require such an executor they get a single one
+     * whose dimensions are chosen such that it does not outperform other system-critical tasks such as garbage
+     * collection and JITting.
+     * <p>
+     * 
+     * The executor will have {@link Thread#NORM_PRIORITY} as its priority, therefore slightly superseding the priority
+     * of {@link #getDefaultBackgroundTaskThreadPoolExecutor()}, and its threads will all be {@link Thread#setDaemon
+     * daemon threads}. The task queue is limited by {@link Integer#MAX_VALUE}, so is virtually unbounded, and therefore
+     * no specific rejection handler is configured.
+     * <p>
+     * 
+     * The thread pool uses constant size, so the core size equals the maximum size, and threads will not be terminated
+     * once created. Its size is calculated using {@link #getReasonableThreadPoolSize()}.
+     */
+    ExecutorService getDefaultForegroundTaskThreadPoolExecutor();
+    
     /**
      * Returns a new thread pool executor that can be used to schedule background tasks. Normally, clients should use
      * {@link #getDefaultBackgroundTaskThreadPoolExecutor()} instead. However, under certain rare circumstances it may

java/com.sap.sse/src/com/sap/sse/util/impl/ThreadPoolUtilImpl.java

@@ -11,12 +11,17 @@ public class ThreadPoolUtilImpl implements ThreadPoolUtil {
     private static final int REASONABLE_THREAD_POOL_SIZE = Math.max(Runtime.getRuntime().availableProcessors()/2, 3);
 
     private final ExecutorService defaultBackgroundTaskThreadPoolExecutor;
+    private final ExecutorService defaultForegroundTaskThreadPoolExecutor;
     
     public ThreadPoolUtilImpl() {
         defaultBackgroundTaskThreadPoolExecutor = new ThreadPoolExecutor(/* corePoolSize */ REASONABLE_THREAD_POOL_SIZE,
                 /* maximumPoolSize */ REASONABLE_THREAD_POOL_SIZE,
                 /* keepAliveTime */ 60, TimeUnit.SECONDS,
                 /* workQueue */ new LinkedBlockingQueue<Runnable>(), new ThreadFactoryWithPriority(Thread.NORM_PRIORITY-1, /* daemon */ true));
+        defaultForegroundTaskThreadPoolExecutor = new ThreadPoolExecutor(/* corePoolSize */ REASONABLE_THREAD_POOL_SIZE,
+                /* maximumPoolSize */ REASONABLE_THREAD_POOL_SIZE,
+                /* keepAliveTime */ 60, TimeUnit.SECONDS,
+                /* workQueue */ new LinkedBlockingQueue<Runnable>(), new ThreadFactoryWithPriority(Thread.NORM_PRIORITY, /* daemon */ true));
     }
     
     @Override
@@ -24,6 +29,11 @@ public class ThreadPoolUtilImpl implements ThreadPoolUtil {
         return defaultBackgroundTaskThreadPoolExecutor;
     }
 
+    @Override
+    public ExecutorService getDefaultForegroundTaskThreadPoolExecutor() {
+        return defaultForegroundTaskThreadPoolExecutor;
+    }
+
     @Override
     public ExecutorService createBackgroundTaskThreadPoolExecutor() {
         return new ThreadPoolExecutor(/* corePoolSize */ REASONABLE_THREAD_POOL_SIZE,