com.softsynth.jmsl.util
Class WeightedObjectChooser

java.lang.Object
  com.softsynth.jmsl.util.WeightedObjectChooser

public class WeightedObjectChooser
extends java.lang.Object

Holds objects and associated weights. Weights are used to govern the likelihood of an object being chosen with next().

Every call to next() first sums the weights, and an object is chosen by comparing a randomly chosen threshold against a running total as objects are enumerated.

For example, the following adds two objects where one is twice as likely to be chosen as the other

 WeightedObjectChooser chooser = new WeightedObjectChooser();
 chooser.addWeightedObject(new Object(), 1.0);
 chooser.addWeightedObject(new Object(), 2.0);
 Object obj = chooser.next();
 

This class was requested by Larry Polansky.

Author:

Nick Didkovsky, email: didkovn@mail.rockefeller.edu, (c) 2004 Nick Didkovsky, all rights reserved.

Constructor Summary

WeightedObjectChooser()

Method Summary

void	addWeightedObject(java.lang.Object object, double weight) Add an Object and associate it with specified weight
boolean	contains(java.lang.Object object)
java.util.Enumeration	elements()
double	getWeight(java.lang.Object object)
static void	main(java.lang.String[] args) source:
java.lang.Object	next()
void	remove(java.lang.Object object) remove specified object from objects under consideration
void	setWeight(java.lang.Object object, double weight) Set weight of an Object.
int	size()
java.lang.String	toString()
double	totalWeights()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

WeightedObjectChooser

public WeightedObjectChooser()

Method Detail

next

public java.lang.Object next()

Returns:

randomly chosen Object, biased by weight

addWeightedObject

public void addWeightedObject(java.lang.Object object,
                              double weight)

Add an Object and associate it with specified weight

setWeight

public void setWeight(java.lang.Object object,
                      double weight)

Set weight of an Object. Adds Object if not already included

getWeight

public double getWeight(java.lang.Object object)

Returns:

weight for specified object. If in doubt use contains() to check first if object is in the chooser

remove

public void remove(java.lang.Object object)

remove specified object from objects under consideration

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

a String listing all objects, their weights, and the percentage of their weights compared to the total weight

totalWeights

public double totalWeights()

Returns:

sum of all weights for all objects in this WeightedObjectChooser

elements

public java.util.Enumeration elements()

Returns:

Enumeration of Objects added to this WeightedObjectChooser

size

public int size()

Returns:

number of objects

contains

public boolean contains(java.lang.Object object)

main

public static void main(java.lang.String[] args)

source:

 public static void main(String args[]) {
     JMSLRandom.randomize();
     WeightedObjectChooser chooser = new WeightedObjectChooser();
     Object gaga1 = new Object();
     Object gaga2 = new Object();
     chooser.addWeightedObject(gaga1, 1.0);
     chooser.addWeightedObject(gaga2, 1.0);
     System.out.println(chooser.toString());
     int gaga1kount = 0;
     int gaga2kount = 0;
     for (int i = 0; i < 100000; i++) {
         Object obj = chooser.next();
         if (obj.equals(gaga1))
             gaga1kount++;
         if (obj.equals(gaga2))
             gaga2kount++;
     }
     System.out.println("gaga1 count=" + gaga1kount + ", gaga2 count=" + gaga2kount);
 }