source: xssim/trunk/src/simulator/stats/random/MinMaxDistribution.java @ 104

package simulator.stats.random;

import cern.jet.random.AbstractDistribution;

/**
 * Represents a wrapper for a specific random distribution class. The purpose of this class is
 * to provide the random values, with a given distribution, but within a given range [min; max] - inclusive. 
 * Min may be called a lower bound, and max an upper bound.
 * @author Stanislaw Szczepanowski
 *
 */
public class MinMaxDistribution extends AbstractDistribution {

        /**
         * The lower bound for the allowed random values (<code>null</code> if no bound was set)
         */
        protected Double min;
        
        /**
         * The upper bound for the allowed random values (<code>null</code> if no bound was set)
         */
        protected Double max;
        
        /**
         * The source distribution for random values
         */
        protected AbstractDistribution source;
        
        /**
         * MinMax constructor. 
         * It constructs the class with a given original distribution and minimal and maximal values.
         * @param origDistribution the original distribution, which will be the source for random numbers. It must not be <code>null</code>.
         * @param min the minimal allowed value for the random numbers. If a <code>null</code> value is given, then no lower bound will be set.
         * @param max the maximal allowed value for the random numbers. If a <code>null</code> value is given, then no upper bound will be set.
         */
        public MinMaxDistribution(AbstractDistribution origDistribution, Double min, Double max) {
                source = origDistribution;
                
                if (min != null && max != null) {
                        if (min > max)
                                throw new IllegalArgumentException("ERROR: invalid parameters min > max");
                }
                
                this.min = min;
                this.max = max;
        }
        
        @Override
        public double nextDouble() {
                double value;
                
                for (;;) {
                        value = source.nextDouble();
                        
                        if (min != null && Double.compare(value, min) < 0)
                                continue;
                        
                        if (max != null && Double.compare(value, max) > 0)
                                continue;

                        break;
                }
                
                return value;
        }
}