Fix missing static imports of TimeUnit

src/main/java/server/TimerManager.java

@@ -30,9 +30,11 @@ import java.lang.management.ManagementFactory;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+
 public class TimerManager implements TimerManagerMBean {
     private static final TimerManager instance = new TimerManager();
 
@@ -69,7 +71,7 @@ public class TimerManager implements TimerManagerMBean {
         stpe.setContinueExistingPeriodicTasksAfterShutdownPolicy(false);
         stpe.setRemoveOnCancelPolicy(true);
 
-        stpe.setKeepAliveTime(5, TimeUnit.MINUTES);
+        stpe.setKeepAliveTime(5, MINUTES);
         stpe.allowCoreThreadTimeOut(true);
 
         ses = stpe;
@@ -87,15 +89,15 @@ public class TimerManager implements TimerManagerMBean {
     }
 
     public ScheduledFuture<?> register(Runnable r, long repeatTime, long delay) {
-        return ses.scheduleAtFixedRate(new LoggingSaveRunnable(r), delay, repeatTime, TimeUnit.MILLISECONDS);
+        return ses.scheduleAtFixedRate(new LoggingSaveRunnable(r), delay, repeatTime, MILLISECONDS);
     }
 
     public ScheduledFuture<?> register(Runnable r, long repeatTime) {
-        return ses.scheduleAtFixedRate(new LoggingSaveRunnable(r), 0, repeatTime, TimeUnit.MILLISECONDS);
+        return ses.scheduleAtFixedRate(new LoggingSaveRunnable(r), 0, repeatTime, MILLISECONDS);
     }
 
     public ScheduledFuture<?> schedule(Runnable r, long delay) {
-        return ses.schedule(new LoggingSaveRunnable(r), delay, TimeUnit.MILLISECONDS);
+        return ses.schedule(new LoggingSaveRunnable(r), delay, MILLISECONDS);
     }
 
     public ScheduledFuture<?> scheduleAtTimestamp(Runnable r, long timestamp) {