clear MidnightTime cache

app/src/main/java/info/nightscout/androidaps/utils/MidnightTime.java

@@ -5,11 +5,13 @@ import android.util.LongSparseArray;
 import java.util.Calendar;
 
 public class MidnightTime {
-    private static final LongSparseArray<Long> times = new LongSparseArray<>();
+    static final LongSparseArray<Long> times = new LongSparseArray<>();
 
     private static long hits = 0;
     private static long misses = 0;
 
+    private static final int THRESHOLD = 100000;
+
     public static long calc() {
         Calendar c = Calendar.getInstance();
         c.set(Calendar.HOUR_OF_DAY, 0);
@@ -36,10 +38,17 @@ public class MidnightTime {
             m = c.getTimeInMillis();
             times.append(time, m);
             ++misses;
+            if (times.size() > THRESHOLD) resetCache();
         }
         return m;
     }
 
+    static void resetCache() {
+        hits = 0;
+        misses = 0;
+        times.clear();
+    }
+
     public static String log() {
         return "Hits: " + hits + " misses: " + misses + " stored: " + times.size();
     }

app/src/test/java/info/nightscout/androidaps/utils/MidnightTimeTest.java

@@ -53,6 +53,13 @@ public class MidnightTimeTest {
         Assert.assertEquals(midnight, MidnightTime.calc(now));
     }
 
+    @Test
+    public void resetCache() {
+        long now = DateUtil.now();
+        MidnightTime.calc(now);
+        MidnightTime.resetCache();
+        Assert.assertEquals(0, MidnightTime.times.size());
+    }
     @Test
     public void log() {
         long now = DateUtil.now();