Problem fixing a new Custom datasource

Hi all:

I need showing a graphic who obtain data from a custom datasource. I see the 
demo sample of datasources in the jasperreports1.2.5 package and I simulate 
that situation, but I don't find the static method in that sample for 
textfield "The static method to call to retrive the JRDataSource" who appears 
in Ireport1.2.5 when I try fixing a new custom datasource(test fail).

Mu custom DataSource sample code is:
package com.emergya.esteve.tcerebral.web.util;

import net.sf.jasperreports.engine.JRDataSource;
import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JRField;


public class SupervivencyDataSource implements JRDataSource
{

private Object[][] data =
{
{new Integer(1), new Float(100)},
{new Integer(2), new Float(98.6)}
};

private int index = -1;


public SupervivencyDataSource()
{
}


public boolean next() throws JRException
{
index++;

return (index < data.length);
}


public Object getFieldValue(JRField field) throws JRException
{
Object value = null;
String fieldName = field.getName();

if ("mounth".equals(fieldName))
{
value = data[index][0];
}
else if ("percent".equals(fieldName))
{
value = data[index][1];
}

return value;
}
}

Any suggestions to resolve? Thank for all

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