Java 8 code cleanup

.travis.yml

@@ -3,9 +3,7 @@ sudo: required
 
 language: java
 
-# This project is aimed to be JRE7-compatible. However, there
-# are issues testing against oraclejdk7 in Travis:
-# https://github.com/travis-ci/travis-ci/issues/7884
+# This project is JRE8-compatible.
 jdk:
   - openjdk8
   - oraclejdk8

DEVELOPER.md

@@ -6,7 +6,7 @@ This document summarizes information relevant to Java tally contributors.
 
 ### Prerequisites
 In order to build this project, you must have:
-- JDK-7 or later
+- JDK-8 or later
 - Apache Thrift 0.9.x -- only if you plan to make changes to Thrift files and recompile (regenerate) source files
 
 ### Building and testing

core/src/main/java/com/uber/m3/tally/BucketPairImpl.java

@@ -28,10 +28,10 @@
  * Default implementation of a {@link BucketPair}
  */
 public class BucketPairImpl implements BucketPair {
-    private double lowerBoundValue;
-    private double upperBoundValue;
-    private Duration lowerBoundDuration;
-    private Duration upperBoundDuration;
+    private final double lowerBoundValue;
+    private final double upperBoundValue;
+    private final Duration lowerBoundDuration;
+    private final Duration upperBoundDuration;
 
     public BucketPairImpl(
         double lowerBoundValue,

core/src/main/java/com/uber/m3/tally/CapableOf.java

@@ -29,8 +29,8 @@ public class CapableOf implements Capabilities {
     public static final CapableOf REPORTING = new CapableOf(true, false);
     public static final CapableOf REPORTING_TAGGING = new CapableOf(true, true);
 
-    private boolean reporting;
-    private boolean tagging;
+    private final boolean reporting;
+    private final boolean tagging;
 
     public CapableOf(boolean reporting, boolean tagging) {
         this.reporting = reporting;
@@ -69,8 +69,8 @@ public boolean equals(Object other) {
     public int hashCode() {
         int code = 0;
 
-        code = 31 * code + new Boolean(reporting).hashCode();
-        code = 31 * code + new Boolean(tagging).hashCode();
+        code = 31 * code + Boolean.valueOf(reporting).hashCode();
+        code = 31 * code + Boolean.valueOf(tagging).hashCode();
 
         return code;
     }

core/src/main/java/com/uber/m3/tally/CounterImpl.java

@@ -28,8 +28,8 @@
  * Default implementation of a {@link Counter}.
  */
 class CounterImpl implements Counter {
-    private AtomicLong prev = new AtomicLong(0);
-    private AtomicLong curr = new AtomicLong(0);
+    private final AtomicLong prev = new AtomicLong(0);
+    private final AtomicLong curr = new AtomicLong(0);
 
     @Override
     public void inc(long delta) {

core/src/main/java/com/uber/m3/tally/CounterSnapshotImpl.java

@@ -28,9 +28,9 @@
  * Default implementation of a {@link CounterSnapshot}.
  */
 class CounterSnapshotImpl implements CounterSnapshot {
-    private String name;
-    private ImmutableMap<String, String> tags;
-    private long value;
+    private final String name;
+    private final ImmutableMap<String, String> tags;
+    private final long value;
 
     CounterSnapshotImpl(String name, ImmutableMap<String, String> tags, long value) {
         this.name = name;

core/src/main/java/com/uber/m3/tally/DurationBuckets.java

@@ -47,7 +47,7 @@ public Double[] asValues() {
 
     @Override
     public Duration[] asDurations() {
-        return buckets.toArray(new Duration[buckets.size()]);
+        return buckets.toArray(new Duration[0]);
     }
 
     /**
@@ -106,7 +106,6 @@ public static DurationBuckets exponential(Duration start, double factor, int num
 
     /**
      * Allows to create bucket with finer bucket creation control
-     *
      * @param sortedDurations sorted values (ascending) of upper bound of the buckets
      * @return {@link DurationBuckets} of the specified parameters
      */

core/src/main/java/com/uber/m3/tally/GaugeImpl.java

@@ -29,8 +29,8 @@
  * Default implementation of a {@link Gauge}.
  */
 class GaugeImpl implements Gauge {
-    private AtomicBoolean updated = new AtomicBoolean(false);
-    private AtomicLong curr = new AtomicLong(0);
+    private final AtomicBoolean updated = new AtomicBoolean(false);
+    private final AtomicLong curr = new AtomicLong(0);
 
     @Override
     public void update(double value) {

core/src/main/java/com/uber/m3/tally/GaugeSnapshotImpl.java

@@ -28,9 +28,9 @@
  * Default implementation of a {@link GaugeSnapshot}.
  */
 class GaugeSnapshotImpl implements GaugeSnapshot {
-    private String name;
-    private ImmutableMap<String, String> tags;
-    private double value;
+    private final String name;
+    private final ImmutableMap<String, String> tags;
+    private final double value;
 
     GaugeSnapshotImpl(String name, ImmutableMap<String, String> tags, double value) {
         this.name = name;

core/src/main/java/com/uber/m3/tally/HistogramImpl.java

@@ -33,13 +33,13 @@
  * Default implementation of a {@link Histogram}.
  */
 class HistogramImpl implements Histogram, StopwatchRecorder {
-    private Type type;
-    private String name;
-    private ImmutableMap<String, String> tags;
-    private Buckets specification;
-    private List<HistogramBucket> buckets;
-    private List<Double> lookupByValue;
-    private List<Duration> lookupByDuration;
+    private final Type type;
+    private final String name;
+    private final ImmutableMap<String, String> tags;
+    private final Buckets specification;
+    private final List<HistogramBucket> buckets;
+    private final List<Double> lookupByValue;
+    private final List<Duration> lookupByDuration;
 
     HistogramImpl(
         String name,
@@ -186,7 +186,7 @@ public void recordStopwatch(long stopwatchStart) {
         recordDuration(Duration.between(stopwatchStart, System.nanoTime()));
     }
 
-    class HistogramBucket {
+    static class HistogramBucket {
         CounterImpl samples;
         double valueLowerBound;
         double valueUpperBound;

core/src/main/java/com/uber/m3/tally/HistogramSnapshotImpl.java

@@ -29,10 +29,10 @@
  * Default implementation of a {@link HistogramSnapshot}.
  */
 class HistogramSnapshotImpl implements HistogramSnapshot {
-    private String name;
-    private ImmutableMap<String, String> tags;
-    private Map<Double, Long> values;
-    private Map<Duration, Long> durations;
+    private final String name;
+    private final ImmutableMap<String, String> tags;
+    private final Map<Double, Long> values;
+    private final Map<Duration, Long> durations;
 
     HistogramSnapshotImpl(
         String name,

core/src/main/java/com/uber/m3/tally/ScopeImpl.java

@@ -33,14 +33,14 @@
  * Default {@link Scope} implementation.
  */
 class ScopeImpl implements Scope {
-    private StatsReporter reporter;
-    private String prefix;
-    private String separator;
-    private ImmutableMap<String, String> tags;
-    private Buckets defaultBuckets;
+    private final StatsReporter reporter;
+    private final String prefix;
+    private final String separator;
+    private final ImmutableMap<String, String> tags;
+    private final Buckets defaultBuckets;
 
-    private ScheduledExecutorService scheduler;
-    private Registry registry;
+    private final ScheduledExecutorService scheduler;
+    private final Registry registry;
 
     // ConcurrentHashMap nearly always allowing read operations seems like a good
     // performance upside to the consequence of reporting a newly-made metric in
@@ -71,15 +71,8 @@ public Counter counter(String name) {
             return counter;
         }
 
-        synchronized (counters) {
-            if (!counters.containsKey(name)) {
-                counters.put(name, new CounterImpl());
-            }
-
-            counter = counters.get(name);
-        }
-
-        return counter;
+        counters.putIfAbsent(name, new CounterImpl());
+        return counters.get(name);
     }
 
     @Override
@@ -90,15 +83,8 @@ public Gauge gauge(String name) {
             return gauge;
         }
 
-        synchronized (gauges) {
-            if (!gauges.containsKey(name)) {
-                gauges.put(name, new GaugeImpl());
-            }
-
-            gauge = gauges.get(name);
-        }
-
-        return gauge;
+        gauges.putIfAbsent(name, new GaugeImpl());
+        return gauges.get(name);
     }
 
     @Override
@@ -109,15 +95,8 @@ public Timer timer(String name) {
             return timer;
         }
 
-        synchronized (timers) {
-            if (!timers.containsKey(name)) {
-                timers.put(name, new TimerImpl(fullyQualifiedName(name), tags, reporter));
-            }
-
-            timer = timers.get(name);
-        }
-
-        return timer;
+        timers.putIfAbsent(name, new TimerImpl(fullyQualifiedName(name), tags, reporter));
+        return timers.get(name);
     }
 
     @Override
@@ -132,15 +111,8 @@ public Histogram histogram(String name, Buckets buckets) {
             return histogram;
         }
 
-        synchronized (histograms) {
-            if (!histograms.containsKey(name)) {
-                histograms.put(name, new HistogramImpl(fullyQualifiedName(name), tags, reporter, buckets));
-            }
-
-            histogram = histograms.get(name);
-        }
-
-        return histogram;
+        histograms.putIfAbsent(name, new HistogramImpl(fullyQualifiedName(name), tags, reporter, buckets));
+        return histograms.get(name);
     }
 
     @Override
@@ -208,11 +180,11 @@ static String keyForPrefixedStringMap(String prefix, ImmutableMap<String, String
         }
 
         if (stringMap == null) {
-            stringMap = ImmutableMap.EMPTY;
+            stringMap = (ImmutableMap<String, String>) ImmutableMap.EMPTY;
         }
 
         Set<String> keySet = stringMap.keySet();
-        String[] sortedKeys = keySet.toArray(new String[keySet.size()]);
+        String[] sortedKeys = keySet.toArray(new String[0]);
         Arrays.sort(sortedKeys);
 
         StringBuilder keyBuffer = new StringBuilder(prefix.length() + sortedKeys.length * 20);

core/src/main/java/com/uber/m3/tally/SnapshotImpl.java

@@ -27,10 +27,10 @@
  * Default implementation of a {@link Snapshot}.
  */
 class SnapshotImpl implements Snapshot {
-    Map<String, CounterSnapshot> counters = new ConcurrentHashMap<>();
-    Map<String, GaugeSnapshot> gauges = new ConcurrentHashMap<>();
-    Map<String, TimerSnapshot> timers = new ConcurrentHashMap<>();
-    Map<String, HistogramSnapshot> histograms = new ConcurrentHashMap<>();
+    private final Map<String, CounterSnapshot> counters = new ConcurrentHashMap<>();
+    private final Map<String, GaugeSnapshot> gauges = new ConcurrentHashMap<>();
+    private final Map<String, TimerSnapshot> timers = new ConcurrentHashMap<>();
+    private final Map<String, HistogramSnapshot> histograms = new ConcurrentHashMap<>();
 
     @Override
     public Map<String, CounterSnapshot> counters() {

core/src/main/java/com/uber/m3/tally/StatsReporter.java

@@ -35,9 +35,9 @@ public interface StatsReporter extends BaseStatsReporter {
      * @param value value to report
      */
     void reportCounter(
-            String name,
-            Map<String, String> tags,
-            long value
+        String name,
+        Map<String, String> tags,
+        long value
     );
 
     /**
@@ -47,9 +47,9 @@ void reportCounter(
      * @param value value to report
      */
     void reportGauge(
-            String name,
-            Map<String, String> tags,
-            double value
+        String name,
+        Map<String, String> tags,
+        double value
     );
 
     /**
@@ -59,9 +59,9 @@ void reportGauge(
      * @param interval interval to report
      */
     void reportTimer(
-            String name,
-            Map<String, String> tags,
-            Duration interval
+        String name,
+        Map<String, String> tags,
+        Duration interval
     );
 
     /**
@@ -74,12 +74,12 @@ void reportTimer(
      * @param samples          samples to report
      */
     void reportHistogramValueSamples(
-            String name,
-            Map<String, String> tags,
-            Buckets buckets,
-            double bucketLowerBound,
-            double bucketUpperBound,
-            long samples
+        String name,
+        Map<String, String> tags,
+        Buckets buckets,
+        double bucketLowerBound,
+        double bucketUpperBound,
+        long samples
     );
 
     /**
@@ -92,11 +92,11 @@ void reportHistogramValueSamples(
      * @param samples          samples to report
      */
     void reportHistogramDurationSamples(
-            String name,
-            Map<String, String> tags,
-            Buckets buckets,
-            Duration bucketLowerBound,
-            Duration bucketUpperBound,
-            long samples
+        String name,
+        Map<String, String> tags,
+        Buckets buckets,
+        Duration bucketLowerBound,
+        Duration bucketUpperBound,
+        long samples
     );
 }

core/src/main/java/com/uber/m3/tally/Stopwatch.java

@@ -27,8 +27,8 @@
  * of the stopwatch are comparable with one another.
  */
 public class Stopwatch {
-    private long startNanos;
-    private StopwatchRecorder recorder;
+    private final long startNanos;
+    private final StopwatchRecorder recorder;
 
     /**
      * Creates a stopwatch.