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.lib;
020    
021    import static com.google.common.base.Preconditions.*;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    import org.apache.hadoop.metrics2.MetricsInfo;
026    
027    /**
028     * The mutable counter (monotonically increasing) metric interface
029     */
030    @InterfaceAudience.Public
031    @InterfaceStability.Evolving
032    public abstract class MutableCounter extends MutableMetric {
033      private final MetricsInfo info;
034    
035      protected MutableCounter(MetricsInfo info) {
036        this.info =  checkNotNull(info, "counter info");
037      }
038    
039      protected MetricsInfo info() {
040        return info;
041      }
042    
043      /**
044       * Increment the metric value by 1.
045       */
046      public abstract void incr();
047    }