feat(jdk8): move files to new folder to avoid resources compiled.

jdkSrc/jdk8/javax/management/monitor/GaugeMonitor.java

@@ -0,0 +1,884 @@
+/*
+ * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package javax.management.monitor;
+
+import static com.sun.jmx.defaults.JmxProperties.MONITOR_LOGGER;
+import java.util.logging.Level;
+import javax.management.MBeanNotificationInfo;
+import javax.management.ObjectName;
+import static javax.management.monitor.Monitor.NumericalType.*;
+import static javax.management.monitor.MonitorNotification.*;
+
+/**
+ * Defines a monitor MBean designed to observe the values of a gauge attribute.
+ *
+ * <P> A gauge monitor observes an attribute that is continuously
+ * variable with time. A gauge monitor sends notifications as
+ * follows:
+ *
+ * <UL>
+ *
+ * <LI> if the attribute value is increasing and becomes equal to or
+ * greater than the high threshold value, a {@link
+ * MonitorNotification#THRESHOLD_HIGH_VALUE_EXCEEDED threshold high
+ * notification} is sent. The notify high flag must be set to
+ * <CODE>true</CODE>.
+ *
+ * <BR>Subsequent crossings of the high threshold value do not cause
+ * further notifications unless the attribute value becomes equal to
+ * or less than the low threshold value.</LI>
+ *
+ * <LI> if the attribute value is decreasing and becomes equal to or
+ * less than the low threshold value, a {@link
+ * MonitorNotification#THRESHOLD_LOW_VALUE_EXCEEDED threshold low
+ * notification} is sent. The notify low flag must be set to
+ * <CODE>true</CODE>.
+ *
+ * <BR>Subsequent crossings of the low threshold value do not cause
+ * further notifications unless the attribute value becomes equal to
+ * or greater than the high threshold value.</LI>
+ *
+ * </UL>
+ *
+ * This provides a hysteresis mechanism to avoid repeated triggering
+ * of notifications when the attribute value makes small oscillations
+ * around the high or low threshold value.
+ *
+ * <P> If the gauge difference mode is used, the value of the derived
+ * gauge is calculated as the difference between the observed gauge
+ * values for two successive observations.
+ *
+ * <BR>The derived gauge value (V[t]) is calculated using the following method:
+ * <UL>
+ * <LI>V[t] = gauge[t] - gauge[t-GP]</LI>
+ * </UL>
+ *
+ * This implementation of the gauge monitor requires the observed
+ * attribute to be of the type integer or floating-point
+ * (<CODE>Byte</CODE>, <CODE>Integer</CODE>, <CODE>Short</CODE>,
+ * <CODE>Long</CODE>, <CODE>Float</CODE>, <CODE>Double</CODE>).
+ *
+ *
+ * @since 1.5
+ */
+public class GaugeMonitor extends Monitor implements GaugeMonitorMBean {
+
+    /*
+     * ------------------------------------------
+     *  PACKAGE CLASSES
+     * ------------------------------------------
+     */
+
+    static class GaugeMonitorObservedObject extends ObservedObject {
+
+        public GaugeMonitorObservedObject(ObjectName observedObject) {
+            super(observedObject);
+        }
+
+        public final synchronized boolean getDerivedGaugeValid() {
+            return derivedGaugeValid;
+        }
+        public final synchronized void setDerivedGaugeValid(
+                                                 boolean derivedGaugeValid) {
+            this.derivedGaugeValid = derivedGaugeValid;
+        }
+        public final synchronized NumericalType getType() {
+            return type;
+        }
+        public final synchronized void setType(NumericalType type) {
+            this.type = type;
+        }
+        public final synchronized Number getPreviousScanGauge() {
+            return previousScanGauge;
+        }
+        public final synchronized void setPreviousScanGauge(
+                                                  Number previousScanGauge) {
+            this.previousScanGauge = previousScanGauge;
+        }
+        public final synchronized int getStatus() {
+            return status;
+        }
+        public final synchronized void setStatus(int status) {
+            this.status = status;
+        }
+
+        private boolean derivedGaugeValid;
+        private NumericalType type;
+        private Number previousScanGauge;
+        private int status;
+    }
+
+    /*
+     * ------------------------------------------
+     *  PRIVATE VARIABLES
+     * ------------------------------------------
+     */
+
+    /**
+     * Gauge high threshold.
+     *
+     * <BR>The default value is a null Integer object.
+     */
+    private Number highThreshold = INTEGER_ZERO;
+
+    /**
+     * Gauge low threshold.
+     *
+     * <BR>The default value is a null Integer object.
+     */
+    private Number lowThreshold = INTEGER_ZERO;
+
+    /**
+     * Flag indicating if the gauge monitor notifies when exceeding
+     * the high threshold.
+     *
+     * <BR>The default value is <CODE>false</CODE>.
+     */
+    private boolean notifyHigh = false;
+
+    /**
+     * Flag indicating if the gauge monitor notifies when exceeding
+     * the low threshold.
+     *
+     * <BR>The default value is <CODE>false</CODE>.
+     */
+    private boolean notifyLow = false;
+
+    /**
+     * Flag indicating if the gauge difference mode is used.  If the
+     * gauge difference mode is used, the derived gauge is the
+     * difference between two consecutive observed values.  Otherwise,
+     * the derived gauge is directly the value of the observed
+     * attribute.
+     *
+     * <BR>The default value is set to <CODE>false</CODE>.
+     */
+    private boolean differenceMode = false;
+
+    private static final String[] types = {
+        RUNTIME_ERROR,
+        OBSERVED_OBJECT_ERROR,
+        OBSERVED_ATTRIBUTE_ERROR,
+        OBSERVED_ATTRIBUTE_TYPE_ERROR,
+        THRESHOLD_ERROR,
+        THRESHOLD_HIGH_VALUE_EXCEEDED,
+        THRESHOLD_LOW_VALUE_EXCEEDED
+    };
+
+    private static final MBeanNotificationInfo[] notifsInfo = {
+        new MBeanNotificationInfo(
+            types,
+            "javax.management.monitor.MonitorNotification",
+            "Notifications sent by the GaugeMonitor MBean")
+    };
+
+    // Flags needed to implement the hysteresis mechanism.
+    //
+    private static final int RISING             = 0;
+    private static final int FALLING            = 1;
+    private static final int RISING_OR_FALLING  = 2;
+
+    /*
+     * ------------------------------------------
+     *  CONSTRUCTORS
+     * ------------------------------------------
+     */
+
+    /**
+     * Default constructor.
+     */
+    public GaugeMonitor() {
+    }
+
+    /*
+     * ------------------------------------------
+     *  PUBLIC METHODS
+     * ------------------------------------------
+     */
+
+    /**
+     * Starts the gauge monitor.
+     */
+    public synchronized void start() {
+        if (isActive()) {
+            MONITOR_LOGGER.logp(Level.FINER, GaugeMonitor.class.getName(),
+                    "start", "the monitor is already active");
+            return;
+        }
+        // Reset values.
+        //
+        for (ObservedObject o : observedObjects) {
+            final GaugeMonitorObservedObject gmo =
+                (GaugeMonitorObservedObject) o;
+            gmo.setStatus(RISING_OR_FALLING);
+            gmo.setPreviousScanGauge(null);
+        }
+        doStart();
+    }
+
+    /**
+     * Stops the gauge monitor.
+     */
+    public synchronized void stop() {
+        doStop();
+    }
+
+    // GETTERS AND SETTERS
+    //--------------------
+
+    /**
+     * Gets the derived gauge of the specified object, if this object is
+     * contained in the set of observed MBeans, or <code>null</code> otherwise.
+     *
+     * @param object the name of the MBean.
+     *
+     * @return The derived gauge of the specified object.
+     *
+     */
+    @Override
+    public synchronized Number getDerivedGauge(ObjectName object) {
+        return (Number) super.getDerivedGauge(object);
+    }
+
+    /**
+     * Gets the derived gauge timestamp of the specified object, if
+     * this object is contained in the set of observed MBeans, or
+     * <code>0</code> otherwise.
+     *
+     * @param object the name of the object whose derived gauge
+     * timestamp is to be returned.
+     *
+     * @return The derived gauge timestamp of the specified object.
+     *
+     */
+    @Override
+    public synchronized long getDerivedGaugeTimeStamp(ObjectName object) {
+        return super.getDerivedGaugeTimeStamp(object);
+    }
+
+    /**
+     * Returns the derived gauge of the first object in the set of
+     * observed MBeans.
+     *
+     * @return The derived gauge.
+     *
+     * @deprecated As of JMX 1.2, replaced by
+     * {@link #getDerivedGauge(ObjectName)}
+     */
+    @Deprecated
+    public synchronized Number getDerivedGauge() {
+        if (observedObjects.isEmpty()) {
+            return null;
+        } else {
+            return (Number) observedObjects.get(0).getDerivedGauge();
+        }
+    }
+
+    /**
+     * Gets the derived gauge timestamp of the first object in the set
+     * of observed MBeans.
+     *
+     * @return The derived gauge timestamp.
+     *
+     * @deprecated As of JMX 1.2, replaced by
+     * {@link #getDerivedGaugeTimeStamp(ObjectName)}
+     */
+    @Deprecated
+    public synchronized long getDerivedGaugeTimeStamp() {
+        if (observedObjects.isEmpty()) {
+            return 0;
+        } else {
+            return observedObjects.get(0).getDerivedGaugeTimeStamp();
+        }
+    }
+
+    /**
+     * Gets the high threshold value common to all observed MBeans.
+     *
+     * @return The high threshold value.
+     *
+     * @see #setThresholds
+     */
+    public synchronized Number getHighThreshold() {
+        return highThreshold;
+    }
+
+    /**
+     * Gets the low threshold value common to all observed MBeans.
+     *
+     * @return The low threshold value.
+     *
+     * @see #setThresholds
+     */
+    public synchronized Number getLowThreshold() {
+        return lowThreshold;
+    }
+
+    /**
+     * Sets the high and the low threshold values common to all
+     * observed MBeans.
+     *
+     * @param highValue The high threshold value.
+     * @param lowValue The low threshold value.
+     *
+     * @exception IllegalArgumentException The specified high/low
+     * threshold is null or the low threshold is greater than the high
+     * threshold or the high threshold and the low threshold are not
+     * of the same type.
+     *
+     * @see #getHighThreshold
+     * @see #getLowThreshold
+     */
+    public synchronized void setThresholds(Number highValue, Number lowValue)
+        throws IllegalArgumentException {
+
+        if ((highValue == null) || (lowValue == null)) {
+            throw new IllegalArgumentException("Null threshold value");
+        }
+
+        if (highValue.getClass() != lowValue.getClass()) {
+            throw new IllegalArgumentException("Different type " +
+                                               "threshold values");
+        }
+
+        if (isFirstStrictlyGreaterThanLast(lowValue, highValue,
+                                           highValue.getClass().getName())) {
+            throw new IllegalArgumentException("High threshold less than " +
+                                               "low threshold");
+        }
+
+        if (highThreshold.equals(highValue) && lowThreshold.equals(lowValue))
+            return;
+        highThreshold = highValue;
+        lowThreshold = lowValue;
+
+        // Reset values.
+        //
+        int index = 0;
+        for (ObservedObject o : observedObjects) {
+            resetAlreadyNotified(o, index++, THRESHOLD_ERROR_NOTIFIED);
+            final GaugeMonitorObservedObject gmo =
+                (GaugeMonitorObservedObject) o;
+            gmo.setStatus(RISING_OR_FALLING);
+        }
+    }
+
+    /**
+     * Gets the high notification's on/off switch value common to all
+     * observed MBeans.
+     *
+     * @return <CODE>true</CODE> if the gauge monitor notifies when
+     * exceeding the high threshold, <CODE>false</CODE> otherwise.
+     *
+     * @see #setNotifyHigh
+     */
+    public synchronized boolean getNotifyHigh() {
+        return notifyHigh;
+    }
+
+    /**
+     * Sets the high notification's on/off switch value common to all
+     * observed MBeans.
+     *
+     * @param value The high notification's on/off switch value.
+     *
+     * @see #getNotifyHigh
+     */
+    public synchronized void setNotifyHigh(boolean value) {
+        if (notifyHigh == value)
+            return;
+        notifyHigh = value;
+    }
+
+    /**
+     * Gets the low notification's on/off switch value common to all
+     * observed MBeans.
+     *
+     * @return <CODE>true</CODE> if the gauge monitor notifies when
+     * exceeding the low threshold, <CODE>false</CODE> otherwise.
+     *
+     * @see #setNotifyLow
+     */
+    public synchronized boolean getNotifyLow() {
+        return notifyLow;
+    }
+
+    /**
+     * Sets the low notification's on/off switch value common to all
+     * observed MBeans.
+     *
+     * @param value The low notification's on/off switch value.
+     *
+     * @see #getNotifyLow
+     */
+    public synchronized void setNotifyLow(boolean value) {
+        if (notifyLow == value)
+            return;
+        notifyLow = value;
+    }
+
+    /**
+     * Gets the difference mode flag value common to all observed MBeans.
+     *
+     * @return <CODE>true</CODE> if the difference mode is used,
+     * <CODE>false</CODE> otherwise.
+     *
+     * @see #setDifferenceMode
+     */
+    public synchronized boolean getDifferenceMode() {
+        return differenceMode;
+    }
+
+    /**
+     * Sets the difference mode flag value common to all observed MBeans.
+     *
+     * @param value The difference mode flag value.
+     *
+     * @see #getDifferenceMode
+     */
+    public synchronized void setDifferenceMode(boolean value) {
+        if (differenceMode == value)
+            return;
+        differenceMode = value;
+
+        // Reset values.
+        //
+        for (ObservedObject o : observedObjects) {
+            final GaugeMonitorObservedObject gmo =
+                (GaugeMonitorObservedObject) o;
+            gmo.setStatus(RISING_OR_FALLING);
+            gmo.setPreviousScanGauge(null);
+        }
+    }
+
+   /**
+     * Returns a <CODE>NotificationInfo</CODE> object containing the
+     * name of the Java class of the notification and the notification
+     * types sent by the gauge monitor.
+     */
+    @Override
+    public MBeanNotificationInfo[] getNotificationInfo() {
+        return notifsInfo.clone();
+    }
+
+    /*
+     * ------------------------------------------
+     *  PRIVATE METHODS
+     * ------------------------------------------
+     */
+
+    /**
+     * Updates the derived gauge attribute of the observed object.
+     *
+     * @param scanGauge The value of the observed attribute.
+     * @param o The observed object.
+     * @return <CODE>true</CODE> if the derived gauge value is valid,
+     * <CODE>false</CODE> otherwise.  The derived gauge value is
+     * invalid when the differenceMode flag is set to
+     * <CODE>true</CODE> and it is the first notification (so we
+     * haven't 2 consecutive values to update the derived gauge).
+     */
+    private synchronized boolean updateDerivedGauge(
+        Object scanGauge, GaugeMonitorObservedObject o) {
+
+        boolean is_derived_gauge_valid;
+
+        // The gauge difference mode is used.
+        //
+        if (differenceMode) {
+
+            // The previous scan gauge has been initialized.
+            //
+            if (o.getPreviousScanGauge() != null) {
+                setDerivedGaugeWithDifference((Number)scanGauge, o);
+                is_derived_gauge_valid = true;
+            }
+            // The previous scan gauge has not been initialized.
+            // We cannot update the derived gauge...
+            //
+            else {
+                is_derived_gauge_valid = false;
+            }
+            o.setPreviousScanGauge((Number)scanGauge);
+        }
+        // The gauge difference mode is not used.
+        //
+        else {
+            o.setDerivedGauge((Number)scanGauge);
+            is_derived_gauge_valid = true;
+        }
+
+        return is_derived_gauge_valid;
+    }
+
+    /**
+     * Updates the notification attribute of the observed object
+     * and notifies the listeners only once if the notify flag
+     * is set to <CODE>true</CODE>.
+     * @param o The observed object.
+     */
+    private synchronized MonitorNotification updateNotifications(
+        GaugeMonitorObservedObject o) {
+
+        MonitorNotification n = null;
+
+        // Send high notification if notifyHigh is true.
+        // Send low notification if notifyLow is true.
+        //
+        if (o.getStatus() == RISING_OR_FALLING) {
+            if (isFirstGreaterThanLast((Number)o.getDerivedGauge(),
+                                       highThreshold,
+                                       o.getType())) {
+                if (notifyHigh) {
+                    n = new MonitorNotification(
+                            THRESHOLD_HIGH_VALUE_EXCEEDED,
+                            this,
+                            0,
+                            0,
+                            "",
+                            null,
+                            null,
+                            null,
+                            highThreshold);
+                }
+                o.setStatus(FALLING);
+            } else if (isFirstGreaterThanLast(lowThreshold,
+                                              (Number)o.getDerivedGauge(),
+                                              o.getType())) {
+                if (notifyLow) {
+                    n = new MonitorNotification(
+                            THRESHOLD_LOW_VALUE_EXCEEDED,
+                            this,
+                            0,
+                            0,
+                            "",
+                            null,
+                            null,
+                            null,
+                            lowThreshold);
+                }
+                o.setStatus(RISING);
+            }
+        } else {
+            if (o.getStatus() == RISING) {
+                if (isFirstGreaterThanLast((Number)o.getDerivedGauge(),
+                                           highThreshold,
+                                           o.getType())) {
+                    if (notifyHigh) {
+                        n = new MonitorNotification(
+                                THRESHOLD_HIGH_VALUE_EXCEEDED,
+                                this,
+                                0,
+                                0,
+                                "",
+                                null,
+                                null,
+                                null,
+                                highThreshold);
+                    }
+                    o.setStatus(FALLING);
+                }
+            } else if (o.getStatus() == FALLING) {
+                if (isFirstGreaterThanLast(lowThreshold,
+                                           (Number)o.getDerivedGauge(),
+                                           o.getType())) {
+                    if (notifyLow) {
+                        n = new MonitorNotification(
+                                THRESHOLD_LOW_VALUE_EXCEEDED,
+                                this,
+                                0,
+                                0,
+                                "",
+                                null,
+                                null,
+                                null,
+                                lowThreshold);
+                    }
+                    o.setStatus(RISING);
+                }
+            }
+        }
+
+        return n;
+    }
+
+    /**
+     * Sets the derived gauge when the differenceMode flag is set to
+     * <CODE>true</CODE>.  Both integer and floating-point types are
+     * allowed.
+     *
+     * @param scanGauge The value of the observed attribute.
+     * @param o The observed object.
+     */
+    private synchronized void setDerivedGaugeWithDifference(
+        Number scanGauge, GaugeMonitorObservedObject o) {
+        Number prev = o.getPreviousScanGauge();
+        Number der;
+        switch (o.getType()) {
+        case INTEGER:
+            der = Integer.valueOf(((Integer)scanGauge).intValue() -
+                                  ((Integer)prev).intValue());
+            break;
+        case BYTE:
+            der = Byte.valueOf((byte)(((Byte)scanGauge).byteValue() -
+                                      ((Byte)prev).byteValue()));
+            break;
+        case SHORT:
+            der = Short.valueOf((short)(((Short)scanGauge).shortValue() -
+                                        ((Short)prev).shortValue()));
+            break;
+        case LONG:
+            der = Long.valueOf(((Long)scanGauge).longValue() -
+                               ((Long)prev).longValue());
+            break;
+        case FLOAT:
+            der = Float.valueOf(((Float)scanGauge).floatValue() -
+                                ((Float)prev).floatValue());
+            break;
+        case DOUBLE:
+            der = Double.valueOf(((Double)scanGauge).doubleValue() -
+                                 ((Double)prev).doubleValue());
+            break;
+        default:
+            // Should never occur...
+            MONITOR_LOGGER.logp(Level.FINEST, GaugeMonitor.class.getName(),
+                    "setDerivedGaugeWithDifference",
+                    "the threshold type is invalid");
+            return;
+        }
+        o.setDerivedGauge(der);
+    }
+
+    /**
+     * Tests if the first specified Number is greater than or equal to
+     * the last.  Both integer and floating-point types are allowed.
+     *
+     * @param greater The first Number to compare with the second.
+     * @param less The second Number to compare with the first.
+     * @param type The number type.
+     * @return <CODE>true</CODE> if the first specified Number is
+     * greater than or equal to the last, <CODE>false</CODE>
+     * otherwise.
+     */
+    private boolean isFirstGreaterThanLast(Number greater,
+                                           Number less,
+                                           NumericalType type) {
+
+        switch (type) {
+        case INTEGER:
+        case BYTE:
+        case SHORT:
+        case LONG:
+            return (greater.longValue() >= less.longValue());
+        case FLOAT:
+        case DOUBLE:
+            return (greater.doubleValue() >= less.doubleValue());
+        default:
+            // Should never occur...
+            MONITOR_LOGGER.logp(Level.FINEST, GaugeMonitor.class.getName(),
+                    "isFirstGreaterThanLast",
+                    "the threshold type is invalid");
+            return false;
+        }
+    }
+
+    /**
+     * Tests if the first specified Number is strictly greater than the last.
+     * Both integer and floating-point types are allowed.
+     *
+     * @param greater The first Number to compare with the second.
+     * @param less The second Number to compare with the first.
+     * @param className The number class name.
+     * @return <CODE>true</CODE> if the first specified Number is
+     * strictly greater than the last, <CODE>false</CODE> otherwise.
+     */
+    private boolean isFirstStrictlyGreaterThanLast(Number greater,
+                                                   Number less,
+                                                   String className) {
+
+        if (className.equals("java.lang.Integer") ||
+            className.equals("java.lang.Byte") ||
+            className.equals("java.lang.Short") ||
+            className.equals("java.lang.Long")) {
+
+            return (greater.longValue() > less.longValue());
+        }
+        else if (className.equals("java.lang.Float") ||
+                 className.equals("java.lang.Double")) {
+
+            return (greater.doubleValue() > less.doubleValue());
+        }
+        else {
+            // Should never occur...
+            MONITOR_LOGGER.logp(Level.FINEST, GaugeMonitor.class.getName(),
+                    "isFirstStrictlyGreaterThanLast",
+                    "the threshold type is invalid");
+            return false;
+        }
+    }
+
+    /*
+     * ------------------------------------------
+     *  PACKAGE METHODS
+     * ------------------------------------------
+     */
+
+    /**
+     * Factory method for ObservedObject creation.
+     *
+     * @since 1.6
+     */
+    @Override
+    ObservedObject createObservedObject(ObjectName object) {
+        final GaugeMonitorObservedObject gmo =
+            new GaugeMonitorObservedObject(object);
+        gmo.setStatus(RISING_OR_FALLING);
+        gmo.setPreviousScanGauge(null);
+        return gmo;
+    }
+
+    /**
+     * This method globally sets the derived gauge type for the given
+     * "object" and "attribute" after checking that the type of the
+     * supplied observed attribute value is one of the value types
+     * supported by this monitor.
+     */
+    @Override
+    synchronized boolean isComparableTypeValid(ObjectName object,
+                                               String attribute,
+                                               Comparable<?> value) {
+        final GaugeMonitorObservedObject o =
+            (GaugeMonitorObservedObject) getObservedObject(object);
+        if (o == null)
+            return false;
+
+        // Check that the observed attribute is either of type
+        // "Integer" or "Float".
+        //
+        if (value instanceof Integer) {
+            o.setType(INTEGER);
+        } else if (value instanceof Byte) {
+            o.setType(BYTE);
+        } else if (value instanceof Short) {
+            o.setType(SHORT);
+        } else if (value instanceof Long) {
+            o.setType(LONG);
+        } else if (value instanceof Float) {
+            o.setType(FLOAT);
+        } else if (value instanceof Double) {
+            o.setType(DOUBLE);
+        } else {
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    synchronized Comparable<?> getDerivedGaugeFromComparable(
+                                                  ObjectName object,
+                                                  String attribute,
+                                                  Comparable<?> value) {
+        final GaugeMonitorObservedObject o =
+            (GaugeMonitorObservedObject) getObservedObject(object);
+        if (o == null)
+            return null;
+
+        // Update the derived gauge attributes and check the
+        // validity of the new value. The derived gauge value
+        // is invalid when the differenceMode flag is set to
+        // true and it is the first notification, i.e. we
+        // haven't got 2 consecutive values to update the
+        // derived gauge.
+        //
+        o.setDerivedGaugeValid(updateDerivedGauge(value, o));
+
+        return (Comparable<?>) o.getDerivedGauge();
+    }
+
+    @Override
+    synchronized void onErrorNotification(MonitorNotification notification) {
+        final GaugeMonitorObservedObject o = (GaugeMonitorObservedObject)
+            getObservedObject(notification.getObservedObject());
+        if (o == null)
+            return;
+
+        // Reset values.
+        //
+        o.setStatus(RISING_OR_FALLING);
+        o.setPreviousScanGauge(null);
+    }
+
+    @Override
+    synchronized MonitorNotification buildAlarmNotification(
+                                               ObjectName object,
+                                               String attribute,
+                                               Comparable<?> value) {
+        final GaugeMonitorObservedObject o =
+            (GaugeMonitorObservedObject) getObservedObject(object);
+        if (o == null)
+            return null;
+
+        // Notify the listeners if the updated derived
+        // gauge value is valid.
+        //
+        final MonitorNotification alarm;
+        if (o.getDerivedGaugeValid())
+            alarm = updateNotifications(o);
+        else
+            alarm = null;
+        return alarm;
+    }
+
+    /**
+     * Tests if the threshold high and threshold low are both of the
+     * same type as the gauge.  Both integer and floating-point types
+     * are allowed.
+     *
+     * Note:
+     *   If the optional lowThreshold or highThreshold have not been
+     *   initialized, their default value is an Integer object with
+     *   a value equal to zero.
+     *
+     * @param object The observed object.
+     * @param attribute The observed attribute.
+     * @param value The sample value.
+     * @return <CODE>true</CODE> if type is the same,
+     * <CODE>false</CODE> otherwise.
+     */
+    @Override
+    synchronized boolean isThresholdTypeValid(ObjectName object,
+                                              String attribute,
+                                              Comparable<?> value) {
+        final GaugeMonitorObservedObject o =
+            (GaugeMonitorObservedObject) getObservedObject(object);
+        if (o == null)
+            return false;
+
+        Class<? extends Number> c = classForType(o.getType());
+        return (isValidForType(highThreshold, c) &&
+                isValidForType(lowThreshold, c));
+    }
+}