001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.metrics2;
020    
021    import com.google.common.base.Objects;
022    import static com.google.common.base.Preconditions.*;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    
027    /**
028     * The immutable metric
029     */
030    @InterfaceAudience.Public
031    @InterfaceStability.Evolving
032    public abstract class AbstractMetric implements MetricsInfo {
033      private final MetricsInfo info;
034    
035      /**
036       * Construct the metric
037       * @param info  about the metric
038       */
039      protected AbstractMetric(MetricsInfo info) {
040        this.info = checkNotNull(info, "metric info");
041      }
042    
043      @Override public String name() {
044        return info.name();
045      }
046    
047      @Override public String description() {
048        return info.description();
049      }
050    
051      protected MetricsInfo info() {
052        return info;
053      }
054    
055      /**
056       * Get the value of the metric
057       * @return the value of the metric
058       */
059      public abstract Number value();
060    
061      /**
062       * Get the type of the metric
063       * @return the type of the metric
064       */
065      public abstract MetricType type();
066    
067      /**
068       * Accept a visitor interface
069       * @param visitor of the metric
070       */
071      public abstract void visit(MetricsVisitor visitor);
072    
073      @Override public boolean equals(Object obj) {
074        if (obj instanceof AbstractMetric) {
075          final AbstractMetric other = (AbstractMetric) obj;
076          return Objects.equal(info, other.info()) &&
077                 Objects.equal(value(), other.value());
078        }
079        return false;
080      }
081    
082      @Override public int hashCode() {
083        return Objects.hashCode(info, value());
084      }
085    
086      @Override public String toString() {
087        return Objects.toStringHelper(this)
088            .add("info", info)
089            .add("value", value())
090            .toString();
091      }
092    }