histogram.java

来自「mysql集群」· Java 代码 · 共 120 行

/*
 * 	This program is free software; you can redistribute it and/or modify it under the terms of 
 * the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, 
 * or (at your option) any later version. 
 * 
 * 	This program 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 for more details. 
 * 	You should have received a copy of the GNU General Public License along with this program; 
 * if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
package com.meidusa.amoeba.util;

import java.util.Arrays;

/**
 * Used for tracking a set of values that fall into a discrete range of
 * values.
 */
public class Histogram
{
    /**
     * Constructs a histogram that will track values with a granularity
     * equal to the <code>bucketWidth</code> from <code>minValue</code> to
     * <code>minValue + bucketWidth*bucketCount</code>.
     */
    public Histogram (int minValue, int bucketWidth, int bucketCount)
    {
        _minValue = minValue;
        _maxValue = minValue + bucketWidth*bucketCount;
        _bucketWidth = bucketWidth;
        _buckets = new int[bucketCount];
    }

    /**
     * Registers a value with this histogram.
     */
    public void addValue (int value)
    {
        if (value < _minValue) {
            _buckets[0]++;
        } else if (value >= _maxValue) {
            _buckets[_buckets.length-1]++;
        } else {
            _buckets[(value-_minValue)/_bucketWidth]++;
        }
        _count++;
    }

    /**
     * Returns the total number of values in the histogram.
     */
    public int size ()
    {
        return _count;
    }

    /**
     * Clears the values from this histogram.
     */
    public void clear ()
    {
        Arrays.fill(_buckets, 0);
    }

    /**
     * Returns the array containing the bucket values. The zeroth element
     * contains the count of all values less than <code>minValue</code>,
     * the subsequent <code>bucketCount</code> elements contain the count
     * of values falling into those buckets and the last element contains
     * values greater than or equal to <code>maxValue</code>.
     */
    public int[] getBuckets ()
    {
        return _buckets;
    }

    /**
     * Generates a terse summary of the count and contents of the values
     * in this histogram.
     */
    public String summarize ()
    {
        StringBuilder buf = new StringBuilder();
        buf.append(_count).append(":");
        for (int ii = 0; ii < _buckets.length; ii++) {
            if (ii > 0) {
                buf.append(",");
            }
            buf.append(_buckets[ii]);
        }
        return buf.toString();
    }

    /**
     * Returns a string representation of this histogram.
     */
    public String toString ()
    {
        return "[min=" + _minValue + ", max=" + _maxValue +
            ", bwidth=" + _bucketWidth +
            ", buckets=" + Arrays.toString(_buckets);
    }

    /** The minimum value tracked by this histogram. */
    protected int _minValue;

    /** The maximum value tracked by this histogram. */
    protected int _maxValue;

    /** The size of each histogram bucket. */
    protected int _bucketWidth;

    /** The total number of values. */
    protected int _count;

    /** The histogram buckets. */
    protected int[] _buckets;
}