001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.management.mbean;
018
019/**
020 * Base implementation of {@link Statistic}
021 * <p/>
022 * The following modes is available:
023 * <ul>
024 * <li>VALUE - A statistic with this update mode is a simple value that is a straight forward
025 * representation of the updated value.</li>
026 * <li>DELTA - A statistic with this update mode is a value that represents the delta
027 * between the last two recorded values (or the initial value if two updates have
028 * not been recorded). This value can be negative if the delta goes up or down.</li>
029 * <li>COUNTER - A statistic with this update mode interprets updates as increments (positive values)
030 * or decrements (negative values) to the current value.</li>
031 * <li>MAXIMUM - A statistic with this update mode is a value that represents the maximum value
032 * amongst the update values applied to this statistic.</li>
033 * <li>MINIMUM - A statistic with this update mode is a value that represents the minimum value
034 * amongst the update values applied to this statistic.</li>
035 * <ul>
036 * The MAXIMUM and MINIMUM modes are not 100% thread-safe as there can be a lost-update problem.
037 * This is on purpose because the performance overhead to ensure atomic updates costs to much
038 * on CPU and memory footprint. The other modes are thread-safe.
039 */
040public abstract class Statistic {
041
042    public abstract void updateValue(long newValue);
043
044    public void increment() {
045        updateValue(1);
046    }
047
048    public void decrement() {
049        updateValue(-1);
050    }
051
052    public abstract long getValue();
053
054    /**
055     * Whether the statistic has been updated one or more times.
056     * Notice this is only working for value, maximum and minimum modes.
057     */
058    public abstract boolean isUpdated();
059
060    public abstract void reset();
061
062}