diff --git a/gradle/ext.gradle b/gradle/ext.gradle
index 2c679b2..df63612 100644
--- a/gradle/ext.gradle
+++ b/gradle/ext.gradle
@@ -1,7 +1,7 @@
 ext {
     user = 'xbib'
     name = 'metrics'
-    description = 'A stripped-down version of Coda Hale Metrics'
+    description = 'A stripped-down and modified version of Coda Hale Metrics'
     scmUrl = 'https://github.com/' + user + '/' + name
     scmConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
     scmDeveloperConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
diff --git a/src/main/java/org/xbib/metrics/Clock.java b/src/main/java/org/xbib/metrics/Clock.java
index dcd2dde..8562ac7 100644
--- a/src/main/java/org/xbib/metrics/Clock.java
+++ b/src/main/java/org/xbib/metrics/Clock.java
@@ -1,20 +1,17 @@
 package org.xbib.metrics;
 
-import java.lang.management.ManagementFactory;
-import java.lang.management.ThreadMXBean;
-
 /**
- * An abstraction for how time passes. It is passed to {@link Sampler} to track timing.
+ * An interface for how time passes. It is passed to {@link Sampler} to track timing.
  */
-public abstract class Clock {
+public interface Clock {
 
     /**
      * The default clock to use.
      *
      * @return the default {@link Clock} instance
-     * @see Clock.UserTimeClock
+     * @see UserTimeClock
      */
-    public static Clock defaultClock() {
+    static Clock defaultClock() {
         return UserTimeClock.DEFAULT;
     }
 
@@ -23,40 +20,13 @@ public abstract class Clock {
      *
      * @return time tick in nanoseconds
      */
-    public abstract long getTick();
+    long getTick();
 
     /**
      * Returns the current time in milliseconds.
      *
      * @return time in milliseconds
      */
-    public long getTime() {
-        return System.currentTimeMillis();
-    }
-
-    /**
-     * A clock implementation which returns the current time in epoch nanoseconds.
-     */
-    public static class UserTimeClock extends Clock {
-        @Override
-        public long getTick() {
-            return System.nanoTime();
-        }
-
-        static final Clock DEFAULT = new UserTimeClock();
-    }
-
-    /**
-     * A clock implementation which returns the current thread's CPU time.
-     */
-    public static class CpuTimeClock extends Clock {
-        private static final ThreadMXBean THREAD_MX_BEAN = ManagementFactory.getThreadMXBean();
-
-        @Override
-        public long getTick() {
-            return THREAD_MX_BEAN.getCurrentThreadCpuTime();
-        }
-    }
-
+    long getTime();
 
 }
diff --git a/src/main/java/org/xbib/metrics/CpuTimeClock.java b/src/main/java/org/xbib/metrics/CpuTimeClock.java
new file mode 100644
index 0000000..05a7669
--- /dev/null
+++ b/src/main/java/org/xbib/metrics/CpuTimeClock.java
@@ -0,0 +1,21 @@
+package org.xbib.metrics;
+
+import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadMXBean;
+
+/**
+ * A clock implementation which returns the current thread's CPU time.
+ */
+class CpuTimeClock implements Clock {
+    private static final ThreadMXBean THREAD_MX_BEAN = ManagementFactory.getThreadMXBean();
+
+    @Override
+    public long getTick() {
+        return THREAD_MX_BEAN.getCurrentThreadCpuTime();
+    }
+
+    @Override
+    public long getTime() {
+        return System.currentTimeMillis();
+    }
+}
diff --git a/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java b/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java
index 45b7fc7..4f30f24 100644
--- a/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java
+++ b/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java
@@ -15,7 +15,8 @@ public class ExpWeightedMovingAverage {
     private static final double M5_ALPHA = 1 - Math.exp(-5 / 60.0 / 5);
     private static final double M15_ALPHA = 1 - Math.exp(-5 / 60.0 / 15);
     private final LongAdder uncounted = new LongAdder();
-    private final double alpha, interval;
+    private final double alpha;
+    private final double interval;
     private volatile boolean initialized = false;
     private volatile double rate = 0.0;
 
diff --git a/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java b/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java
index f6e1bb8..c0b2325 100644
--- a/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java
+++ b/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java
@@ -72,10 +72,12 @@ public class ExponentiallyDecayingReservoir implements Reservoir {
         this.nextScaleTime = new AtomicLong(clock.getTick() + RESCALE_THRESHOLD);
     }
 
+    @Override
     public int size() {
         return (int) min(size, count.get());
     }
 
+    @Override
     public void update(long value) {
         update(value, currentTimeInSeconds());
     }
@@ -119,6 +121,7 @@ public class ExponentiallyDecayingReservoir implements Reservoir {
         }
     }
 
+    @Override
     public Snapshot getSnapshot() {
         lockForRegularUsage();
         try {
diff --git a/src/main/java/org/xbib/metrics/Gauge.java b/src/main/java/org/xbib/metrics/Gauge.java
index 3f23f18..f3f53ad 100644
--- a/src/main/java/org/xbib/metrics/Gauge.java
+++ b/src/main/java/org/xbib/metrics/Gauge.java
@@ -14,6 +14,7 @@ package org.xbib.metrics;
  *
  * @param <T> the type of the metric's value
  */
+@FunctionalInterface
 public interface Gauge<T> extends Metric {
     /**
      * Returns the metric's current value.
diff --git a/src/main/java/org/xbib/metrics/Histogram.java b/src/main/java/org/xbib/metrics/Histogram.java
index 2a6916e..4f4beda 100644
--- a/src/main/java/org/xbib/metrics/Histogram.java
+++ b/src/main/java/org/xbib/metrics/Histogram.java
@@ -40,7 +40,7 @@ public class Histogram implements Metric, Sampling, Count {
 
     @Override
     public void inc(String index, String type, String id) {
-
+        // not used
     }
 
     @Override
@@ -55,7 +55,7 @@ public class Histogram implements Metric, Sampling, Count {
 
     @Override
     public void dec(String index, String type, String id) {
-
+        // not used
     }
 
     /**
diff --git a/src/main/java/org/xbib/metrics/Meter.java b/src/main/java/org/xbib/metrics/Meter.java
index e7458f4..04839fd 100644
--- a/src/main/java/org/xbib/metrics/Meter.java
+++ b/src/main/java/org/xbib/metrics/Meter.java
@@ -46,12 +46,7 @@ public class Meter implements Metered {
 
     public void spawn(long intervalSeconds) {
         this.future = Executors.newScheduledThreadPool(1)
-                .scheduleAtFixedRate(new Runnable() {
-                    @Override
-                    public void run() {
-                        tickIfNecessary();
-                    }
-                }, intervalSeconds, intervalSeconds, TimeUnit.SECONDS);
+                .scheduleAtFixedRate(this::tickIfNecessary, intervalSeconds, intervalSeconds, TimeUnit.SECONDS);
     }
 
     public void stop() {
diff --git a/src/main/java/org/xbib/metrics/MetricFilter.java b/src/main/java/org/xbib/metrics/MetricFilter.java
index d18915d..0be8511 100644
--- a/src/main/java/org/xbib/metrics/MetricFilter.java
+++ b/src/main/java/org/xbib/metrics/MetricFilter.java
@@ -3,16 +3,12 @@ package org.xbib.metrics;
 /**
  * A filter used to determine whether or not a metric should be reported, among other things.
  */
+@FunctionalInterface
 public interface MetricFilter {
     /**
      * Matches all metrics, regardless of type or name.
      */
-    MetricFilter ALL = new MetricFilter() {
-        @Override
-        public boolean matches(MetricName name, Metric metric) {
-            return true;
-        }
-    };
+    MetricFilter ALL = (name, metric) -> true;
 
     /**
      * Returns {@code true} if the metric matches the filter; {@code false} otherwise.
diff --git a/src/main/java/org/xbib/metrics/MetricName.java b/src/main/java/org/xbib/metrics/MetricName.java
index 34b150a..0ef8668 100644
--- a/src/main/java/org/xbib/metrics/MetricName.java
+++ b/src/main/java/org/xbib/metrics/MetricName.java
@@ -41,7 +41,7 @@ public class MetricName implements Comparable<MetricName> {
      **/
     public static MetricName join(MetricName... parts) {
         final StringBuilder nameBuilder = new StringBuilder();
-        final Map<String, String> tags = new HashMap<String, String>();
+        final Map<String, String> tags = new HashMap<>();
 
         boolean first = true;
 
@@ -92,16 +92,13 @@ public class MetricName implements Comparable<MetricName> {
             if (name == null || name.isEmpty()) {
                 continue;
             }
-
             if (first) {
                 first = false;
             } else {
                 builder.append(SEPARATOR);
             }
-
             builder.append(name);
         }
-
         return builder.toString();
     }
 
@@ -109,7 +106,6 @@ public class MetricName implements Comparable<MetricName> {
         if (tags == null || tags.isEmpty()) {
             return EMPTY_TAGS;
         }
-
         return Collections.unmodifiableMap(tags);
     }
 
@@ -132,7 +128,6 @@ public class MetricName implements Comparable<MetricName> {
      */
     public MetricName resolve(String p) {
         final String next;
-
         if (p != null && !p.isEmpty()) {
             if (key != null && !key.isEmpty()) {
                 next = key + SEPARATOR + p;
@@ -142,7 +137,6 @@ public class MetricName implements Comparable<MetricName> {
         } else {
             next = this.key;
         }
-
         return new MetricName(next, tags);
     }
 
@@ -153,9 +147,9 @@ public class MetricName implements Comparable<MetricName> {
      * @return A newly created metric name with the specified tags associated with it.
      */
     public MetricName tagged(Map<String, String> add) {
-        final Map<String, String> tags = new HashMap<String, String>(add);
-        tags.putAll(this.tags);
-        return new MetricName(key, tags);
+        final Map<String, String> map = new HashMap<>(add);
+        map.putAll(this.tags);
+        return new MetricName(key, map);
     }
 
     /**
@@ -171,17 +165,13 @@ public class MetricName implements Comparable<MetricName> {
         if (pairs == null) {
             return this;
         }
-
         if (pairs.length % 2 != 0) {
             throw new IllegalArgumentException("Argument count must be even");
         }
-
-        final Map<String, String> add = new HashMap<String, String>();
-
+        final Map<String, String> add = new HashMap<>();
         for (int i = 0; i < pairs.length; i += 2) {
             add.put(pairs[i], pairs[i + 1]);
         }
-
         return tagged(add);
     }
 
@@ -189,9 +179,7 @@ public class MetricName implements Comparable<MetricName> {
     public String toString() {
         if (tags.isEmpty()) {
             return key;
-            //return key + "{}";
         }
-
         return key + tags;
     }
 
@@ -209,17 +197,13 @@ public class MetricName implements Comparable<MetricName> {
         if (this == obj) {
             return true;
         }
-
         if (obj == null) {
             return false;
         }
-
         if (getClass() != obj.getClass()) {
             return false;
         }
-
         MetricName other = (MetricName) obj;
-
         if (key == null) {
             if (other.key != null) {
                 return false;
@@ -227,23 +211,15 @@ public class MetricName implements Comparable<MetricName> {
         } else if (!key.equals(other.key)) {
             return false;
         }
-
         return tags.equals(other.tags);
-
     }
 
     @Override
     public int compareTo(MetricName o) {
-        if (o == null) {
-            return -1;
-        }
-
         int c = compareName(key, o.getKey());
-
         if (c != 0) {
             return c;
         }
-
         return compareTags(tags, o.getTags());
     }
 
@@ -251,15 +227,12 @@ public class MetricName implements Comparable<MetricName> {
         if (left == null && right == null) {
             return 0;
         }
-
         if (left == null) {
             return 1;
         }
-
         if (right == null) {
             return -1;
         }
-
         return left.compareTo(right);
     }
 
@@ -267,45 +240,35 @@ public class MetricName implements Comparable<MetricName> {
         if (left == null && right == null) {
             return 0;
         }
-
         if (left == null) {
             return 1;
         }
-
         if (right == null) {
             return -1;
         }
-
         final Iterable<String> keys = uniqueSortedKeys(left, right);
-
-        for (final String key : keys) {
-            final String a = left.get(key);
-            final String b = right.get(key);
-
+        for (final String s : keys) {
+            final String a = left.get(s);
+            final String b = right.get(s);
             if (a == null && b == null) {
                 continue;
             }
-
             if (a == null) {
                 return -1;
             }
-
             if (b == null) {
                 return 1;
             }
-
             int c = a.compareTo(b);
-
             if (c != 0) {
                 return c;
             }
         }
-
         return 0;
     }
 
     private Iterable<String> uniqueSortedKeys(Map<String, String> left, Map<String, String> right) {
-        final Set<String> set = new TreeSet<String>(left.keySet());
+        final Set<String> set = new TreeSet<>(left.keySet());
         set.addAll(right.keySet());
         return set;
     }
diff --git a/src/main/java/org/xbib/metrics/MetricRegistry.java b/src/main/java/org/xbib/metrics/MetricRegistry.java
index 501d3b1..43842cb 100644
--- a/src/main/java/org/xbib/metrics/MetricRegistry.java
+++ b/src/main/java/org/xbib/metrics/MetricRegistry.java
@@ -10,12 +10,15 @@ import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 /**
  * A registry of metric instances.
  */
 public class MetricRegistry implements MetricSet {
 
+    private static final Logger logger = Logger.getLogger(MetricRegistry.class.getName());
     private final ConcurrentMap<MetricName, Metric> metrics;
     private final List<MetricRegistryListener> listeners;
 
@@ -23,7 +26,7 @@ public class MetricRegistry implements MetricSet {
      * Creates a new {@link MetricRegistry}.
      */
     public MetricRegistry() {
-        this(new ConcurrentHashMap<MetricName, Metric>());
+        this(new ConcurrentHashMap<>());
     }
 
     /**
@@ -35,7 +38,7 @@ public class MetricRegistry implements MetricSet {
      */
     protected MetricRegistry(ConcurrentMap<MetricName, Metric> metricsMap) {
         this.metrics = metricsMap;
-        this.listeners = new CopyOnWriteArrayList<MetricRegistryListener>();
+        this.listeners = new CopyOnWriteArrayList<>();
     }
 
     /**
@@ -68,7 +71,9 @@ public class MetricRegistry implements MetricSet {
         }
         final String[] parts = new String[length + 1];
         parts[0] = name;
-        System.arraycopy(names, 0, parts, 1, length);
+        if (names != null) {
+            System.arraycopy(names, 0, parts, 1, length);
+        }
         return MetricName.build(parts);
     }
 
@@ -80,7 +85,7 @@ public class MetricRegistry implements MetricSet {
      * @see #register(MetricName, Metric)
      */
     @SuppressWarnings("unchecked")
-    public <T extends Metric> T register(String name, T metric) throws IllegalArgumentException {
+    public <T extends Metric> T register(String name, T metric) {
         return register(MetricName.build(name), metric);
     }
 
@@ -94,7 +99,7 @@ public class MetricRegistry implements MetricSet {
      * @throws IllegalArgumentException if the name is already registered
      */
     @SuppressWarnings("unchecked")
-    public <T extends Metric> T register(MetricName name, T metric) throws IllegalArgumentException {
+    public <T extends Metric> T register(MetricName name, T metric) {
         if (metric instanceof MetricSet) {
             registerAll(name, (MetricSet) metric);
         } else {
@@ -115,7 +120,7 @@ public class MetricRegistry implements MetricSet {
      * @param metrics a set of metrics
      * @throws IllegalArgumentException if any of the names are already registered
      */
-    public void registerAll(MetricSet metrics) throws IllegalArgumentException {
+    public void registerAll(MetricSet metrics) {
         registerAll(null, metrics);
     }
 
@@ -368,6 +373,7 @@ public class MetricRegistry implements MetricSet {
             try {
                 return register(name, builder.newMetric());
             } catch (IllegalArgumentException e) {
+                logger.log(Level.WARNING, e.getMessage(), e);
                 final Metric added = metrics.get(name);
                 if (builder.isInstance(added)) {
                     return (T) added;
@@ -379,7 +385,7 @@ public class MetricRegistry implements MetricSet {
 
     @SuppressWarnings("unchecked")
     private <T extends Metric> SortedMap<MetricName, T> getMetrics(Class<T> klass, MetricFilter filter) {
-        final TreeMap<MetricName, T> timers = new TreeMap<MetricName, T>();
+        final TreeMap<MetricName, T> timers = new TreeMap<>();
         for (Map.Entry<MetricName, Metric> entry : metrics.entrySet()) {
             if (klass.isInstance(entry.getValue()) && filter.matches(entry.getKey(),
                     entry.getValue())) {
@@ -433,11 +439,8 @@ public class MetricRegistry implements MetricSet {
         }
     }
 
-    private void registerAll(MetricName prefix, MetricSet metrics) throws IllegalArgumentException {
-        if (prefix == null) {
-            prefix = MetricName.EMPTY;
-        }
-
+    private void registerAll(MetricName prefixName, MetricSet metrics) {
+        MetricName prefix = prefixName == null ? MetricName.EMPTY : prefixName;
         for (Map.Entry<MetricName, Metric> entry : metrics.getMetrics().entrySet()) {
             if (entry.getValue() instanceof MetricSet) {
                 registerAll(MetricName.join(prefix, entry.getKey()), (MetricSet) entry.getValue());
diff --git a/src/main/java/org/xbib/metrics/MetricSet.java b/src/main/java/org/xbib/metrics/MetricSet.java
index 10b5662..7a6ead4 100644
--- a/src/main/java/org/xbib/metrics/MetricSet.java
+++ b/src/main/java/org/xbib/metrics/MetricSet.java
@@ -7,6 +7,7 @@ import java.util.Map;
  *
  * @see MetricRegistry#registerAll(MetricSet)
  */
+@FunctionalInterface
 public interface MetricSet extends Metric {
     /**
      * A map of metric names to metrics.
diff --git a/src/main/java/org/xbib/metrics/Sampling.java b/src/main/java/org/xbib/metrics/Sampling.java
index 0600d38..793225e 100644
--- a/src/main/java/org/xbib/metrics/Sampling.java
+++ b/src/main/java/org/xbib/metrics/Sampling.java
@@ -3,6 +3,7 @@ package org.xbib.metrics;
 /**
  * An object which samples values.
  */
+@FunctionalInterface
 public interface Sampling {
     /**
      * Returns a snapshot of the values.
diff --git a/src/main/java/org/xbib/metrics/Snapshot.java b/src/main/java/org/xbib/metrics/Snapshot.java
index 5628245..c6e1ca3 100644
--- a/src/main/java/org/xbib/metrics/Snapshot.java
+++ b/src/main/java/org/xbib/metrics/Snapshot.java
@@ -3,9 +3,9 @@ package org.xbib.metrics;
 import java.io.OutputStream;
 
 /**
- * A statistical snapshot of a {@link Snapshot}.
+ * A {@link Snapshot}.
  */
-public abstract class Snapshot {
+public interface Snapshot {
 
     /**
      * Returns the value at the given quantile.
@@ -13,109 +13,97 @@ public abstract class Snapshot {
      * @param quantile a given quantile, in {@code [0..1]}
      * @return the value in the distribution at {@code quantile}
      */
-    public abstract double getValue(double quantile);
+    double getValue(double quantile);
 
     /**
      * Returns the entire set of values in the snapshot.
      *
      * @return the entire set of values
      */
-    public abstract long[] getValues();
+    long[] getValues();
 
     /**
      * Returns the number of values in the snapshot.
      *
      * @return the number of values
      */
-    public abstract int size();
+    int size();
 
     /**
      * Returns the median value in the distribution.
      *
      * @return the median value
      */
-    public double getMedian() {
-        return getValue(0.5);
-    }
+    double getMedian();
 
     /**
      * Returns the value at the 75th percentile in the distribution.
      *
      * @return the value at the 75th percentile
      */
-    public double get75thPercentile() {
-        return getValue(0.75);
-    }
+    double get75thPercentile();
 
     /**
      * Returns the value at the 95th percentile in the distribution.
      *
      * @return the value at the 95th percentile
      */
-    public double get95thPercentile() {
-        return getValue(0.95);
-    }
+    double get95thPercentile();
 
     /**
      * Returns the value at the 98th percentile in the distribution.
      *
      * @return the value at the 98th percentile
      */
-    public double get98thPercentile() {
-        return getValue(0.98);
-    }
+    double get98thPercentile();
 
     /**
      * Returns the value at the 99th percentile in the distribution.
      *
      * @return the value at the 99th percentile
      */
-    public double get99thPercentile() {
-        return getValue(0.99);
-    }
+    double get99thPercentile();
 
     /**
      * Returns the value at the 99.9th percentile in the distribution.
      *
      * @return the value at the 99.9th percentile
      */
-    public double get999thPercentile() {
-        return getValue(0.999);
-    }
+    double get999thPercentile();
 
     /**
      * Returns the highest value in the snapshot.
      *
      * @return the highest value
      */
-    public abstract long getMax();
+    long getMax();
 
     /**
      * Returns the arithmetic mean of the values in the snapshot.
      *
      * @return the arithmetic mean
      */
-    public abstract double getMean();
+    double getMean();
 
     /**
      * Returns the lowest value in the snapshot.
      *
      * @return the lowest value
      */
-    public abstract long getMin();
+    long getMin();
 
     /**
      * Returns the standard deviation of the values in the snapshot.
      *
      * @return the standard value
      */
-    public abstract double getStdDev();
+    double getStdDev();
 
     /**
      * Writes the values of the snapshot to the given stream.
      *
      * @param output an output stream
      */
-    public abstract void dump(OutputStream output);
+    void dump(OutputStream output);
 
 }
diff --git a/src/main/java/org/xbib/metrics/UserTimeClock.java b/src/main/java/org/xbib/metrics/UserTimeClock.java
new file mode 100644
index 0000000..3b229d4
--- /dev/null
+++ b/src/main/java/org/xbib/metrics/UserTimeClock.java
@@ -0,0 +1,20 @@
+package org.xbib.metrics;
+
+/**
+ * A clock implementation which returns the current time in epoch nanoseconds.
+ */
+class UserTimeClock implements Clock {
+
+    static final Clock DEFAULT = new UserTimeClock();
+
+    @Override
+    public long getTick() {
+        return System.nanoTime();
+    }
+
+    @Override
+    public long getTime() {
+        return System.currentTimeMillis();
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/org/xbib/metrics/WeightedSnapshot.java b/src/main/java/org/xbib/metrics/WeightedSnapshot.java
index 6c096c4..493a291 100644
--- a/src/main/java/org/xbib/metrics/WeightedSnapshot.java
+++ b/src/main/java/org/xbib/metrics/WeightedSnapshot.java
@@ -6,12 +6,11 @@ import java.io.PrintWriter;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Comparator;
 
 /**
  * A statistical snapshot of a {@link WeightedSnapshot}.
  */
-public class WeightedSnapshot extends Snapshot {
+public class WeightedSnapshot implements Snapshot {
 
     private final long[] values;
     private final double[] normWeights;
@@ -25,31 +24,28 @@ public class WeightedSnapshot extends Snapshot {
     public WeightedSnapshot(Collection<WeightedSample> values) {
         final WeightedSample[] copy = values.toArray(new WeightedSample[]{});
 
-        Arrays.sort(copy, new Comparator<WeightedSample>() {
-            @Override
-            public int compare(WeightedSample o1, WeightedSample o2) {
-                if (o1.value > o2.value) {
-                    return 1;
-                }
-                if (o1.value < o2.value) {
-                    return -1;
-                }
-                return 0;
+        Arrays.sort(copy, (o1, o2) -> {
+            if (o1.value > o2.value) {
+                return 1;
             }
+            if (o1.value < o2.value) {
+                return -1;
+            }
+            return 0;
         });
 
         this.values = new long[copy.length];
         this.normWeights = new double[copy.length];
         this.quantiles = new double[copy.length];
 
-        double sumWeight = 0;
+        double sumWeight = 0.0f;
         for (WeightedSample sample : copy) {
             sumWeight += sample.weight;
         }
 
         for (int i = 0; i < copy.length; i++) {
             this.values[i] = copy[i].value;
-            this.normWeights[i] = copy[i].weight / sumWeight;
+            this.normWeights[i] = safeDivide(copy[i].weight, sumWeight);
         }
 
         for (int i = 1; i < copy.length; i++) {
@@ -57,6 +53,88 @@ public class WeightedSnapshot extends Snapshot {
         }
     }
 
+    private static double safeDivide(double dividend, double divisor) {
+        if (Double.compare(divisor, Double.NaN) == 0) {
+            return Double.NaN;
+        }
+        if (Double.compare(dividend, Double.NaN) == 0) {
+            return Double.NaN;
+        }
+        if (Double.compare(divisor, 0.0) == 0) {
+            if (Double.compare(dividend, 0.0) == -1) {
+                return Double.NEGATIVE_INFINITY;
+            }
+            return Double.POSITIVE_INFINITY;
+        }
+        if (Double.compare(divisor, -0.0) == 0) {
+            if (Double.compare(dividend, -0.0) == 1) {
+                return Double.NEGATIVE_INFINITY;
+            }
+            return Double.POSITIVE_INFINITY;
+        }
+        return dividend / divisor;
+    }
+
+    /**
+     * Returns the median value in the distribution.
+     *
+     * @return the median value
+     */
+    @Override
+    public double getMedian() {
+        return getValue(0.5);
+    }
+
+    /**
+     * Returns the value at the 75th percentile in the distribution.
+     *
+     * @return the value at the 75th percentile
+     */
+    @Override
+    public double get75thPercentile() {
+        return getValue(0.75);
+    }
+
+    /**
+     * Returns the value at the 95th percentile in the distribution.
+     *
+     * @return the value at the 95th percentile
+     */
+    @Override
+    public double get95thPercentile() {
+        return getValue(0.95);
+    }
+
+    /**
+     * Returns the value at the 98th percentile in the distribution.
+     *
+     * @return the value at the 98th percentile
+     */
+    @Override
+    public double get98thPercentile() {
+        return getValue(0.98);
+    }
+
+    /**
+     * Returns the value at the 99th percentile in the distribution.
+     *
+     * @return the value at the 99th percentile
+     */
+    @Override
+    public double get99thPercentile() {
+        return getValue(0.99);
+    }
+
+    /**
+     * Returns the value at the 99.9th percentile in the distribution.
+     *
+     * @return the value at the 99.9th percentile
+     */
+    @Override
+    public double get999thPercentile() {
+        return getValue(0.999);
+    }
+
     /**
      * Returns the value at the given quantile.
      *