Enable PrivateConstructorForUtilityClass Error Prone warning.

This commit also adds some private constructors to utility and example classes.

10 files changed, 16 insertions, 1 deletions

diff --git a/api/src/main/java/io/opencensus/common/TimeUtil.java b/api/src/main/java/io/opencensus/common/TimeUtil.java
index ab64c5df..09b3ddf9 100644
--- a/api/src/main/java/io/opencensus/common/TimeUtil.java
+++ b/api/src/main/java/io/opencensus/common/TimeUtil.java
@@ -23,4 +23,6 @@ final class TimeUtil {
   static final long MILLIS_PER_SECOND = 1000L;
   static final long NANOS_PER_MILLI = 1000 * 1000;
   static final long NANOS_PER_SECOND = NANOS_PER_MILLI * MILLIS_PER_SECOND;
+
+  private TimeUtil() {}
 }
diff --git a/api/src/main/java/io/opencensus/internal/Provider.java b/api/src/main/java/io/opencensus/internal/Provider.java
index 25cb82b0..8cfb7294 100644
--- a/api/src/main/java/io/opencensus/internal/Provider.java
+++ b/api/src/main/java/io/opencensus/internal/Provider.java
@@ -28,6 +28,7 @@ import java.util.ServiceConfigurationError;
  * }</pre>
  */
 public final class Provider {
+  private Provider() {}
 
   /**
    * Tries to create an instance of the given rawClass as a subclass of the given superclass.
diff --git a/contrib/agent/src/main/java/io/opencensus/contrib/agent/Resources.java b/contrib/agent/src/main/java/io/opencensus/contrib/agent/Resources.java
index f0725443..7367b85a 100644
--- a/contrib/agent/src/main/java/io/opencensus/contrib/agent/Resources.java
+++ b/contrib/agent/src/main/java/io/opencensus/contrib/agent/Resources.java
@@ -30,6 +30,7 @@ import java.io.OutputStream;
 
 /** Helper methods for working with resources. */
 final class Resources {
+  private Resources() {}
 
   /**
    * Returns a resource of the given name as a temporary file.
diff --git a/examples/src/main/java/io/opencensus/examples/stats/StatsRunner.java b/examples/src/main/java/io/opencensus/examples/stats/StatsRunner.java
index e9839025..18060204 100644
--- a/examples/src/main/java/io/opencensus/examples/stats/StatsRunner.java
+++ b/examples/src/main/java/io/opencensus/examples/stats/StatsRunner.java
@@ -46,6 +46,8 @@ public class StatsRunner {
   private static final Tagger tagger = Tags.getTagger();
   private static final StatsRecorder statsRecorder = Stats.getStatsRecorder();
 
+  private StatsRunner() {}
+
   /**
    * Main method.
    *
diff --git a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
index 317567b6..19ec285c 100644
--- a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
+++ b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
@@ -30,6 +30,8 @@ public final class MultiSpansContextTracing {
   // Per class Tracer.
   private static final Tracer tracer = Tracing.getTracer();
 
+  private MultiSpansContextTracing() {}
+
   private static void doSomeOtherWork() {
     tracer.getCurrentSpan().addAnnotation("Annotation to the child Span");
   }
diff --git a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
index d3e4bd97..9cfdb665 100644
--- a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
+++ b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
@@ -30,6 +30,8 @@ public final class MultiSpansScopedTracing {
   // Per class Tracer.
   private static final Tracer tracer = Tracing.getTracer();
 
+  private MultiSpansScopedTracing() {}
+
   private static void doSomeOtherWork() {
     tracer.getCurrentSpan().addAnnotation("Annotation to the child Span");
   }
diff --git a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansTracing.java b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansTracing.java
index 20cfe35d..0f6fdd84 100644
--- a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansTracing.java
+++ b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansTracing.java
@@ -26,6 +26,8 @@ public final class MultiSpansTracing {
   // Per class Tracer.
   private static final Tracer tracer = Tracing.getTracer();
 
+  private MultiSpansTracing() {}
+
   private static void doWork() {
     Span rootSpan = tracer.spanBuilderWithExplicitParent("MyRootSpan", null).startSpan();
     rootSpan.addAnnotation("Annotation to the root Span before child is created.");
diff --git a/examples/src/main/java/io/opencensus/examples/zpages/ZPagesTester.java b/examples/src/main/java/io/opencensus/examples/zpages/ZPagesTester.java
index 61e135dd..56825097 100644
--- a/examples/src/main/java/io/opencensus/examples/zpages/ZPagesTester.java
+++ b/examples/src/main/java/io/opencensus/examples/zpages/ZPagesTester.java
@@ -20,6 +20,8 @@ import io.opencensus.contrib.zpages.ZPageHandlers;
 
 /** Testing only class for the UI. */
 public class ZPagesTester {
+  private ZPagesTester() {}
+
   /** Main method. */
   public static void main(String[] args) throws Exception {
     ZPageHandlers.startHttpServerAndRegisterAll(8080);
diff --git a/gradle/errorprone/experimental_suggestions b/gradle/errorprone/experimental_suggestions
index 7ef3a2ad..d68ec9a8 100644
--- a/gradle/errorprone/experimental_suggestions
+++ b/gradle/errorprone/experimental_suggestions
@@ -7,7 +7,7 @@ errorProneExperimentalSuggestions = \
 -Xep:MultipleTopLevelClasses:ERROR,\
 -Xep:PackageLocation:ERROR,\
 -Xep:PrivateConstructorForNoninstantiableModuleTest:ERROR,\
--Xep:PrivateConstructorForUtilityClass:OFF,\
+-Xep:PrivateConstructorForUtilityClass:ERROR,\
 -Xep:RemoveUnusedImports:ERROR,\
 -Xep:ThrowsUncheckedException:ERROR,\
 -Xep:UnnecessaryStaticImport:ERROR,\
diff --git a/impl_core/src/test/java/io/opencensus/implcore/tags/TagsTestUtil.java b/impl_core/src/test/java/io/opencensus/implcore/tags/TagsTestUtil.java
index c64eced1..dcfba508 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/tags/TagsTestUtil.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/tags/TagsTestUtil.java
@@ -24,6 +24,7 @@ import java.util.Collection;
 
 /** Test utilities for tagging. */
 public class TagsTestUtil {
+  private TagsTestUtil() {}
 
   /** Returns a collection of all tags in a {@link TagContext}. */
   public static Collection<Tag> tagContextToList(TagContext tags) {