java - soot issue...counting the jimple line numbers??

Hello everybody,

I am trying to write a program that takes a java class file...converts it into corresponding jimple code and prints out the jimple statements along with their line numbers. Then I would like to pick out those lines from the jimple code which have a "virtual invoke". The code that I have written looks like below:

Code :

import soot.*;
import java.util.*;
import soot.util.*;
import soot.jimple.Stmt;
import soot.tagkit.LineNumberTag;
import soot.baf.*;
import java.io.*;
 
public class GetStmts4 extends BodyTransformer implements RetInst
{
    private static GetStmts4 instance = new GetStmts4();
 
    private GetStmts4() {};
 
    public static GetStmts4 v()
    {
    return instance;
    }
 
    public static void main(String args[])
    {
    soot.options.Options.v().set_keep_line_number(true);
    //soot.options.Options.v().set_whole_program(true);
    //soot.options.Options.v().setPhaseOption("cg","verbose:true");
        PackManager.v().getPack("jtp").add(new Transform ("jtp.annotexample",GetStmts4.v()));
    soot.Main.main(args);
 
    }
 
    protected void internalTransform(Body b, String phaseName, Map options)
    {
    int linenum = 0;
    int count = 0;
    int array[] = new int[20];
    PatchingChain units = b.getUnits();
    Iterator unitsIt = units.iterator();
 
    while(unitsIt.hasNext())
        {
        Unit unit = (Unit)unitsIt.next();
        LineNumberTag tag = (LineNumberTag) unit.getTag("LineNumberTag");
        int index = rt.getIndex();  //to get the index of the jimple line??is this correct??
        System.out.println("Index is :" + index);
       System.out.println(unit);
        if (tag != null)
 
//wrote the following piece of code but it gives me the line number in the source code...and not the jimple line number
            {
            System.out.println("java line number:"+tag.getLineNumber());
            //System.out.println("tag name:"+tag.getName());
            String string = unit.toString();
            if(string.matches("\\s*.*virtualinvoke.*"))
                {
                count++;
                System.out.println("line number with virtualinvoke:"+tag.getLineNumber());
                array[count] = tag.getLineNumber();
                System.out.println("the " +count+ " element in array is : " +array[count]);
                }
            }
        }
    for(int k = 1;k <= count; k++)
        {
        System.out.println(array[k]);
        }
      }
   }

I am getting the following error:
GetStmts4.java:9: GetStmts4 is not abstract and does not override abstract method setIndex(int) in soot.baf.RetInst
public class GetStmts4 extends BodyTransformer implements RetInst
^

Would be really grateful if somebody could help me out with this.
Thanks!!!