Java Programming

Hello,
I try to make a small application which use hibernate to comunicate with database.The problem is the following:
At a momment I have this situation:
In my values.hbm.xml file:

<hibernate-mapping >
 <class lazy="false" name="BusinessProject.Medie" table="MyValues">
    <id column="ID" name="ID" type="integer">
      <generator class="identity"/>
    </id>
    <property name="FirstNumber" type="double">
      <column name="No1"/>
    </property>
    <property name="SecondNumber" type="double">
      <column name="No2"/>
    </property>
    <property name="ThirdNumber" type="double">
      <column name="No3"/>
    </property>
   <property name="MA" type="double">
      <column name="MA"/>
    </property>
    <property name="MG" type="double">
      <column name="MG"/>
    </property>
 </class>
</hibernate-mapping>

the following code is the mapped class:

public class Medie implements IMedie
{
    double dblfirstnumber,dblsecondnumber,dblthirdnumber;
    double dblMA,dblMG;
    int intID;
    SaveMedie objSaveMedie = new SaveMedie();
    Medii objLoadMedie = new Medii();
    Flag flag;
   ArrayList<Error> arrAllErrors = new ArrayList<Error>();
    public double getFirstNumber()
    {
    	flag = new Flag(false);
    	return dblfirstnumber;
    }
    public double getSecondNumber()
    {
    	flag = new Flag(false);
    	return dblsecondnumber;
    }

    public double getThirdNumber()
    {
    	flag = new Flag(false);
    	return dblthirdnumber;
    }

    public double getMA()
    {
	    return dblMA;
    }

    public double getMG()
    {
	    return dblMG;
    }
    public void setFirstNumber(double dblfirstnumber)
    {
    	flag = new Flag(true);
    	this.dblfirstnumber=dblfirstnumber;
    	if ((dblfirstnumber < 20)||(dblfirstnumber > 150))
		{
		    Error e = new Error();
		    e.setErrorNumber(0);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("FirstNumber");
		    arrAllErrors.add(e);
		}
    }
    public void setSecondNumber(double dblsecondnumber)
    {
    	flag = new Flag(true); 
    	this.dblsecondnumber=dblsecondnumber;	
    	if ((dblsecondnumber < 20)||(dblsecondnumber > 150))
		{
		    Error e = new Error();
		    e.setErrorNumber(0);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("SecondNumber");
		    arrAllErrors.add(e);
		}
    	if (dblsecondnumber == this.getFirstNumber())
		{
    		Error e = new Error();
		    e.setErrorNumber(1);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("FirstNumber");
		    arrAllErrors.add(e);
		}
    }
    public void setThirdNumber(double dblthirdnumber)
    {
        flag = new Flag(true);
	if ((dblthirdnumber < 20)||(dblthirdnumber > 150))
		{
		    Error e = new Error();
		    e.setErrorNumber(0);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("ThirdNumber");
		    arrAllErrors.add(e);
		}
	if (dblthirdnumber == this.getFirstNumber())
		{
		    Error e = new Error();
		    e.setErrorNumber(3);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("ThirdNumber");
		    arrAllErrors.add(e);
		}
	 if (dblthirdnumber == this.getSecondNumber())
		{
		    Error e = new Error();
		    e.setErrorNumber(2);
		    e.setErrorString(RelatedFunctions.readerrFromFile(e.getErrorNumber()));
		    e.setProperty("SecondNumber");
		    arrAllErrors.add(e);
		}
	this.dblthirdnumber=dblthirdnumber;
    }

    public void setMA(double dblMA)
    {
    	this.dblMA=dblMA;
    }
    
    public void setMG(double dblMG)
    {
    	this.dblMG=dblMG;
    }
    
    
    public void setID(int l)
    {
    	this.intID=l;
    }
    
    public int getID()
    {
    	return intID;
    }
   
    public double MAritm(double dblfirst,double dblsecond, double dblthird)
    {
        return (dblfirst+dblsecond+dblthird)/3;
    }
   
    public double MGeom(double dblfirst,double dblsecond,double dblthird)
    {
        return Math.pow(dblfirst*dblsecond*dblthird,0.33);
    }
  
    public void LoadFromDB()
    {
	  objSaveMedie.LoadFromDB();
    }
   
    public Medii getarr()
    {
    	return objLoadMedie.loadFromDB();
    }
   public Medie()
   {
  
   }
    
   public Medie(int intID)
    {
    	this.LoadByID(intID); 
    }
   
   public Medie LoadByID(int intID)
   	{
   		return this.objSaveMedie.LoadFromDBbyID(intID);
   	}
    public ArrayList<Error> getErrarr()
    {
    	return this.arrAllErrors;
    }
    public boolean isEmptyCollection()
    {
	if (this.arrAllErrors.size()==0)
	    return true;
	return false;
    }
    public void updateDatabase(Medie objMedie)
    {	
    	this.objSaveMedie.UpdateDB(this);
    }
}

As you can see I use in the hibernate mapping file the property called "FirstNumber" but the properties in the class is : setFirstNumber and getFirstNumber.If I rename my

properties in the class like in mapping file ("FirstNumber" e.g), to use the polymorphism ,then the application is not running.
Tell me please that issue is a hibernate restriction or something I made worng...


Many thanks,

Julian A.