1 files changed, 99 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/stats/Measurement.java b/api/src/main/java/io/opencensus/stats/Measurement.java
new file mode 100644
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--- /dev/null
+++ b/api/src/main/java/io/opencensus/stats/Measurement.java
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2016-17, OpenCensus Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.stats;
+
+import com.google.auto.value.AutoValue;
+import io.opencensus.common.Function;
+import io.opencensus.stats.Measure.MeasureDouble;
+import io.opencensus.stats.Measure.MeasureLong;
+import javax.annotation.concurrent.Immutable;
+
+/** Immutable representation of a Measurement. */
+@Immutable
+public abstract class Measurement {
+
+  /**
+   * Applies the given match function to the underlying data type.
+   */
+  public abstract <T> T match(
+      Function<? super MeasurementDouble, T> p0,
+      Function<? super MeasurementLong, T> p1,
+      Function<? super Measurement, T> defaultFunction);
+
+  /**
+   * Extracts the measured {@link Measure}.
+   */
+  public abstract Measure getMeasure();
+
+  // Prevents this class from being subclassed anywhere else.
+  private Measurement() {
+  }
+
+  /** {@code Double} typed {@link Measurement}. */
+  @Immutable
+  @AutoValue
+  public abstract static class MeasurementDouble extends Measurement {
+    MeasurementDouble() {}
+
+    /**
+     * Constructs a new {@link MeasurementDouble}.
+     */
+    public static MeasurementDouble create(MeasureDouble measure, double value) {
+      return new AutoValue_Measurement_MeasurementDouble(measure, value);
+    }
+
+    @Override
+    public abstract MeasureDouble getMeasure();
+
+    public abstract double getValue();
+
+    @Override
+    public <T> T match(
+        Function<? super MeasurementDouble, T> p0,
+        Function<? super MeasurementLong, T> p1,
+        Function<? super Measurement, T> defaultFunction) {
+      return p0.apply(this);
+    }
+  }
+
+  /** {@code Long} typed {@link Measurement}. */
+  @Immutable
+  @AutoValue
+  public abstract static class MeasurementLong extends Measurement {
+    MeasurementLong() {}
+
+    /**
+     * Constructs a new {@link MeasurementLong}.
+     */
+    public static MeasurementLong create(MeasureLong measure, long value) {
+      return new AutoValue_Measurement_MeasurementLong(measure, value);
+    }
+
+    @Override
+    public abstract MeasureLong getMeasure();
+
+    public abstract long getValue();
+
+    @Override
+    public <T> T match(
+        Function<? super MeasurementDouble, T> p0,
+        Function<? super MeasurementLong, T> p1,
+        Function<? super Measurement, T> defaultFunction) {
+      return p1.apply(this);
+    }
+  }
+}