diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/Count.java b/java/runtime/src/main/java/io/ray/runtime/metric/Count.java
index 986af6c5e..19b75f851 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/Count.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/Count.java
@@ -17,7 +17,7 @@ public class Count extends Metric {
     super(name, tags);
     count = new DoubleAdder();
     metricNativePointer = NativeMetric.registerCountNative(name, description, unit,
-      tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
+        tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
     Preconditions.checkState(metricNativePointer != 0, "Count native pointer must not be 0.");
   }
 
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/Gauge.java b/java/runtime/src/main/java/io/ray/runtime/metric/Gauge.java
index 330349337..63b4c7c28 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/Gauge.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/Gauge.java
@@ -13,7 +13,7 @@ public class Gauge extends Metric {
   public Gauge(String name, String description, String unit, Map<TagKey, String> tags) {
     super(name, tags);
     metricNativePointer = NativeMetric.registerGaugeNative(name, description, unit,
-      tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
+        tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
     Preconditions.checkState(metricNativePointer != 0, "Gauge native pointer must not be 0.");
   }
 
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/Histogram.java b/java/runtime/src/main/java/io/ray/runtime/metric/Histogram.java
index 1b506cdfe..5260f4101 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/Histogram.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/Histogram.java
@@ -22,8 +22,8 @@ public class Histogram extends Metric {
                    Map<TagKey, String> tags) {
     super(name, tags);
     metricNativePointer = NativeMetric.registerHistogramNative(name, description, unit,
-      boundaries.stream().mapToDouble(Double::doubleValue).toArray(),
-      tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
+        boundaries.stream().mapToDouble(Double::doubleValue).toArray(),
+        tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
     Preconditions.checkState(metricNativePointer != 0,
         "Histogram native pointer must not be 0.");
     histogramWindow = Collections.synchronizedList(new ArrayList<>());
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/Metric.java b/java/runtime/src/main/java/io/ray/runtime/metric/Metric.java
index c89ef37a9..271a93f84 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/Metric.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/Metric.java
@@ -32,6 +32,7 @@ public abstract class Metric {
   // Sync metric with core worker stats for registry.
   // Metric data will be flushed into stats view data inside core worker immediately after
   // record is called.
+
   /**
    * Flush records to stats in last aggregator.
    */
@@ -51,19 +52,24 @@ public abstract class Metric {
 
   /**
    * Get the value to record and then reset.
+   *
    * @return latest updating value.
    */
   protected abstract double getAndReset();
 
-  /** Update gauge value without tags.
+  /**
+   * Update gauge value without tags.
    * Update metric info for user.
+   *
    * @param value latest value for updating
    */
   public abstract void update(double value);
 
-  /** Update gauge value with dynamic tag values.
+  /**
+   * Update gauge value with dynamic tag values.
+   *
    * @param value latest value for updating
-   * @param tags tag map
+   * @param tags  tag map
    */
   public void update(double value, Map<TagKey, String> tags) {
     update(value);
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/MetricConfig.java b/java/runtime/src/main/java/io/ray/runtime/metric/MetricConfig.java
index 825178fa4..f7890b096 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/MetricConfig.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/MetricConfig.java
@@ -39,10 +39,10 @@ public class MetricConfig {
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this)
-      .add("timeIntervalMs", timeIntervalMs)
-      .add("threadPoolSize", threadPoolSize)
-      .add("shutdownWaitTimeMs", shutdownWaitTimeMs)
-      .toString();
+        .add("timeIntervalMs", timeIntervalMs)
+        .add("threadPoolSize", threadPoolSize)
+        .add("shutdownWaitTimeMs", shutdownWaitTimeMs)
+        .toString();
   }
 
   public static MetricConfigBuilder builder() {
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/MetricId.java b/java/runtime/src/main/java/io/ray/runtime/metric/MetricId.java
index 07e27cc0b..9c6fa9165 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/MetricId.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/MetricId.java
@@ -32,8 +32,8 @@ public class MetricId {
     }
     MetricId metricId = (MetricId) o;
     return type == metricId.type &&
-      Objects.equals(name, metricId.name) &&
-      Objects.equals(tags, metricId.tags);
+        Objects.equals(name, metricId.name) &&
+        Objects.equals(tags, metricId.tags);
   }
 
   @Override
@@ -44,10 +44,10 @@ public class MetricId {
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this)
-      .add("type", type)
-      .add("name", name)
-      .add("tags", tags)
-      .toString();
+        .add("type", type)
+        .add("name", name)
+        .add("tags", tags)
+        .toString();
   }
 
   public MetricType getType() {
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/MetricRegistry.java b/java/runtime/src/main/java/io/ray/runtime/metric/MetricRegistry.java
index 7d6649d3e..20288512a 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/MetricRegistry.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/MetricRegistry.java
@@ -125,7 +125,7 @@ public class MetricRegistry {
       return MetricType.HISTOGRAM;
     }
     throw new RuntimeException(
-      "Unknown metric type, the metric is " + metric.getClass().getSimpleName());
+        "Unknown metric type, the metric is " + metric.getClass().getSimpleName());
   }
 
   private MetricId genMetricIdByMetric(Metric metric) {
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/MetricType.java b/java/runtime/src/main/java/io/ray/runtime/metric/MetricType.java
index 0f9c772d2..6455fa624 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/MetricType.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/MetricType.java
@@ -11,6 +11,6 @@ public enum MetricType {
 
   SUM,
 
-  HISTOGRAM;
+  HISTOGRAM
 
 }
\ No newline at end of file
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/NativeMetric.java b/java/runtime/src/main/java/io/ray/runtime/metric/NativeMetric.java
index 0d85e91ee..8f6e077cc 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/NativeMetric.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/NativeMetric.java
@@ -26,6 +26,4 @@ class NativeMetric {
 
   public static native void unregisterMetricNative(long gaugePtr);
 
-
-
 }
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/Sum.java b/java/runtime/src/main/java/io/ray/runtime/metric/Sum.java
index e42425011..6ad8b833f 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/Sum.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/Sum.java
@@ -17,7 +17,7 @@ public class Sum extends Metric {
   public Sum(String name, String description, String unit, Map<TagKey, String> tags) {
     super(name, tags);
     metricNativePointer = NativeMetric.registerSumNative(name, description, unit,
-      tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
+        tags.keySet().stream().map(TagKey::getTagKey).collect(Collectors.toList()));
     Preconditions.checkState(metricNativePointer != 0, "Count native pointer must not be 0.");
     this.sum = new DoubleAdder();
   }
diff --git a/java/runtime/src/main/java/io/ray/runtime/metric/TagKey.java b/java/runtime/src/main/java/io/ray/runtime/metric/TagKey.java
index 731417f9f..494c505c0 100644
--- a/java/runtime/src/main/java/io/ray/runtime/metric/TagKey.java
+++ b/java/runtime/src/main/java/io/ray/runtime/metric/TagKey.java
@@ -10,7 +10,7 @@ public class TagKey {
   private String tagKey;
 
   public TagKey(String key) {
-    tagKey =  key;
+    tagKey = key;
     NativeMetric.registerTagkeyNative(key);
   }
 
@@ -38,7 +38,7 @@ public class TagKey {
   @Override
   public String toString() {
     return "TagKey{" +
-      ", tagKey='" + tagKey + '\'' +
-      '}';
+        ", tagKey='" + tagKey + '\'' +
+        '}';
   }
 }
\ No newline at end of file
diff --git a/java/test/src/main/java/io/ray/test/MetricTest.java b/java/test/src/main/java/io/ray/test/MetricTest.java
index ca7496e97..50aba6819 100644
--- a/java/test/src/main/java/io/ray/test/MetricTest.java
+++ b/java/test/src/main/java/io/ray/test/MetricTest.java
@@ -28,49 +28,49 @@ public class MetricTest extends BaseTest {
                                       int threadPoolSize,
                                       long shutdownWaitTimeMs) {
     MetricConfig config = MetricConfig.builder()
-      .timeIntervalMs(timeIntervalMs)
-      .threadPoolSize(threadPoolSize)
-      .shutdownWaitTimeMs(shutdownWaitTimeMs)
-      .create();
+        .timeIntervalMs(timeIntervalMs)
+        .threadPoolSize(threadPoolSize)
+        .shutdownWaitTimeMs(shutdownWaitTimeMs)
+        .create();
     Metrics.init(config);
     return config;
   }
 
   private Gauge registerGauge() {
     return Metrics.gauge()
-      .name("metric_gauge")
-      .description("gauge")
-      .unit("")
-      .tags(ImmutableMap.of("tag1", "value1"))
-      .register();
+        .name("metric_gauge")
+        .description("gauge")
+        .unit("")
+        .tags(ImmutableMap.of("tag1", "value1"))
+        .register();
   }
 
   private Count registerCount() {
     return Metrics.count()
-      .name("metric_count")
-      .description("counter")
-      .unit("1pc")
-      .tags(ImmutableMap.of("tag1", "value1", "count_tag", "default"))
-      .register();
+        .name("metric_count")
+        .description("counter")
+        .unit("1pc")
+        .tags(ImmutableMap.of("tag1", "value1", "count_tag", "default"))
+        .register();
   }
 
   private Sum registerSum() {
     return Metrics.sum()
-      .name("metric_sum")
-      .description("sum")
-      .unit("1pc")
-      .tags(ImmutableMap.of("tag1", "value1", "sum_tag", "default"))
-      .register();
+        .name("metric_sum")
+        .description("sum")
+        .unit("1pc")
+        .tags(ImmutableMap.of("tag1", "value1", "sum_tag", "default"))
+        .register();
   }
 
   private Histogram registerHistogram() {
     return Metrics.histogram()
-      .name("metric_histogram")
-      .description("histogram")
-      .unit("1pc")
-      .boundaries(ImmutableList.of(10.0, 15.0, 20.0))
-      .tags(ImmutableMap.of("tag1", "value1", "histogram_tag", "default"))
-      .register();
+        .name("metric_histogram")
+        .description("histogram")
+        .unit("1pc")
+        .boundaries(ImmutableList.of(10.0, 15.0, 20.0))
+        .tags(ImmutableMap.of("tag1", "value1", "histogram_tag", "default"))
+        .register();
   }
 
   @AfterMethod
@@ -122,7 +122,7 @@ public class MetricTest extends BaseTest {
     boundaries.add(15.0);
     boundaries.add(12.0);
     Histogram histogram = new Histogram("metric_histogram", "histogram", "1pc",
-      boundaries, tags);
+        boundaries, tags);
     for (int i = 1; i <= 200; ++i) {
       histogram.update(i * 1.0d);
     }