Something

import com.sun.org.apache.bcel.internal.classfile.ClassParser;
import com.sun.org.apache.bcel.internal.classfile.JavaClass;
import com.sun.org.apache.bcel.internal.classfile.Method;
import com.sun.org.apache.bcel.internal.classfile.Field;
import com.sun.org.apache.bcel.internal.classfile.Attribute;
import com.sun.org.apache.bcel.internal.generic.*;
import com.sun.org.apache.bcel.internal.util.InstructionFinder;
import com.sun.org.apache.bcel.internal.Constants;

import java.lang.instrument.ClassFileTransformer;
import java.security.ProtectionDomain;
import java.io.ByteArrayInputStream;
import java.util.Iterator;

public class Transformer implements ClassFileTransformer
{

 gui mainFrame	= new gui();

    public byte[] transform(
            ClassLoader loader,
            String className,
            Class<?> classBeingRedefined,
            ProtectionDomain protectionDomain,
            byte[] classFileBuffer)
    {
       // mainFrame.add("Starting javaagent");
        mainFrame.add(className);
        if (className.contains("ath"))
        {
            mainFrame.add("Into Math class");
            try
            {
                ClassGen clazz = new ClassGen(new ClassParser(new ByteArrayInputStream(classFileBuffer), null).parse());
                ConstantPoolGen cpg = clazz.getConstantPool();
                for (Method m : clazz.getMethods())
                {

                    if(m.getName().equals("random"))
                    {
                        mainFrame.add("Found the Math class and the random() function");
//                    MethodGen methodGen = new MethodGen(m, className,cpg);
//                    InstructionList il = methodGen.getInstructionList();
//                    Iterator<InstructionHandle> ilit = il.iterator();
//                    while (ilit.hasNext())
//                    {
//                        Instruction instruction = ilit.next().getInstruction();
//                        if (instruction instanceof SIPUSH)
//                        {
//                            int val = ((SIPUSH) (instruction)).getValue().intValue();
//                            if (val < 400 || val > 800 || val == 503 || val == 765)
//                            {
//                                continue;
//                            }
//                            mainFrame.add("Client Version: "+ val);
//                        }
//                    }
                    }
                }       // !for
            }        // !try
            catch (Exception e)
            {
                e.printStackTrace();
                return classFileBuffer;
            }
        }
        return classFileBuffer;
    }   // !function



}   // !class