diff --git a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/CapabilityHook.java b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/CapabilityHook.java
index 0f28260c6..e780c572a 100644
--- a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/CapabilityHook.java
+++ b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/CapabilityHook.java
@@ -28,7 +28,7 @@ import java.util.Map;
  */
 public abstract class CapabilityHook<T> implements MetricRegistryListener {
 
-    private Map<String,T> capables = new HashMap<>();
+    private final Map<String,T> capables = new HashMap<>();
 
     public abstract void onCapableAdded(String name, T capable);
     public abstract void onCapableRemoved(String name, T capable);
diff --git a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/HdrDeltaHistogramAttachment.java b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/HdrDeltaHistogramAttachment.java
index 50eeff2c6..30641bf65 100644
--- a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/HdrDeltaHistogramAttachment.java
+++ b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/HdrDeltaHistogramAttachment.java
@@ -46,5 +46,5 @@ public interface HdrDeltaHistogramAttachment extends HdrDeltaHistogramProvider {
      * Attach a metric.
      * @return the attached metric, after adding to the mirrors for the metric.
      */
-    public HdrDeltaHistogramProvider attachHdrDeltaHistogram();
+    HdrDeltaHistogramProvider attachHdrDeltaHistogram();
 }
diff --git a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/NicerHistogram.java b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/NicerHistogram.java
index 8bff7992b..1e6f17cfa 100644
--- a/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/NicerHistogram.java
+++ b/nb-api/src/main/java/io/nosqlbench/engine/api/metrics/NicerHistogram.java
@@ -28,7 +28,7 @@ public class NicerHistogram extends Histogram implements DeltaSnapshotter, HdrDe
     private final DeltaHdrHistogramReservoir hdrDeltaReservoir;
     private long cacheExpiryMillis = 0L;
     private long cacheTimeMillis = 0L;
-    private String metricName;
+    private final String metricName;
     private List<Histogram> mirrors;
 
     public NicerHistogram(String metricName, DeltaHdrHistogramReservoir hdrHistogramReservoir) {