Extending Your Applications with Bean Scripting Framework

Listing 1

package stat;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.Collections;

import java.util.HashMap;

public class Stats {

public ArrayList nums;

public Stats(ArrayList someNums){

nums = new ArrayList(someNums);

}

public Stats(double[] someNums){

nums = new ArrayList(someNums.length);

for (int index=0; index  < someNums.length; index++){

nums.add(new Double(someNums[index]));

}

}

public double getMean (){

return this.getMean(true);

}

public double getMean (boolean sample){

// Define mean that finds two types of mean, namely:

// population mean and sample mean

double sum=0.0;

double average=0.0;

Iterator iterator = nums.iterator();

while(iterator.hasNext())

sum = sum + ((Double)iterator.next()).doubleValue();

// Check to see if this is a sample mean

if(sample)

average = sum / nums.size()-1;

else

average = sum / nums.size();

return average;

}

public ArrayList getRange (){

// Find the range. Returns a tuple with the minimum,

// maximum, and range value

double min, max;

ArrayList ranges;

min = ((Double)Collections.min(nums)).doubleValue();

max = ((Double)Collections.max(nums)).doubleValue();

ranges = new ArrayList();

ranges.add(new Double (min));

ranges.add(new Double (max));

ranges.add(new Double (max-min));

return ranges;

}

public double getMedian (){

// Find the Median number

// create a duplicate since we are going to modify the 

   // sequence

ArrayList seq = new ArrayList(nums);

// sort the list of numbers

Collections.sort(seq);

double median = 0.0; // to hold the median value

int length = seq.size(); // to hold the length of the 

                         // sequence

int index=0;

// Check to see if the length is an even number

if ( ( length % 2) == 0){

// since it is an even number

// add the two middle number together

index = length / 2;

double m1 = ((Double)seq.get(index-1)).doubleValue();

double m2 = ((Double)seq.get(index)).doubleValue();

median = (m1 + m2) /2.0;

}

else{

// since it is an odd number

// just grab the middle number

index = (length / 2);

median = ((Double)seq.get(index)).doubleValue();

}

return median;

}

private int countMode(Object object, ArrayList list){

int index = 0;

int count = 0;

do {

index = Collections.binarySearch(list, object);

if(index >=0)list.remove(index);

count++;

}

while (index >=0);

return count;

}

public double getMode (){

// Find the number that repeats the most.

// make a duplicate copy of the nums argument

ArrayList duplicate = new ArrayList(nums);

Collections.sort(duplicate);

double highest_count = -100;

double mode = -100;

Iterator iterator = nums.iterator();

// iterate through nums removing each item out of the duplicate

// calculate the highest_count and the mode

while(iterator.hasNext()){

double count = 0;

Object item = iterator.next();

// Count the number of times the item occurs in the list

// If Count is 0 go to the next iteration

count = countMode(item, duplicate);

if (count == 0) continue;

// determine the highest count. The highest counted item is the mode.

if (count > highest_count){

highest_count = count;

mode = ((Double)item).doubleValue();

}

}

return mode;

}

}

Listing 2

print "The mode of the houses is %2.2f" %  houses.mode

print "The mean of the houses is %2.2f" % houses.mean

print "The median of the houses is %2.2f" % houses.median

Listing 3

import com.ibm.cs.util.IOUtils;

import com.ibm.bsf.BSFManager;

import com.ibm.bsf.BSFEngine;

import java.io.FileReader;

import stat.Stats;

class Test {

public static void main (String [] args){

BSFManager manager = new BSFManager ();

//Register JPython into the scripting manager.

String[] extensions = {"py"};

manager.registerScriptingEngine ("jpython",

"com.ibm.bsf.engines.jpython.JPythonEngine",

extensions);

try{

//Load JPython engine

BSFEngine jpythonEngine = manager.loadScriptingEngine ("jpython");

//Execute an expression.

Object result = manager.eval ("jpython", "testString", 0, 0, "2+32");

System.out.println("eval="+result);

//Map some objects that the script will use.

double[] houses=new double [] {100.0e3, 130.0e3, 140e3, 150e3};

Stats stats = new Stats(houses);

manager.declareBean("houses", stats, Stats.class);

//Load the script and execute it.

String fileName = "TestStat2.py";

String language = manager.getLangFromFilename(fileName);

String script = IOUtils.getStringFromReader(new FileReader(fileName));

manager.exec(language, fileName, 0, 0, script);

}//try

catch (Exception e){

System.out.println(""+e);

}//catch

}//main

}//Test