traverse a dir, search some text and do some thing

import java.io.*;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
         
public class traverseDir {
    public static void main(String[] args) {
        if(args.length != 2) {
            System.out.println("Invalid parameters!");
            return;
        }
        String scanDir = args[0];
        String packageSuffix = args[1];
        try {
            traverseDir td = new traverseDir();
            lf.listFile(scanDir, packageSuffix);
        } catch (ArrayIndexOutOfBoundsException ea) {
            System.out.println("Usage: ListFiles <source dir> <target file>");
        } catch (Exception e) {
            System.out.println("IO error!/r/n"+e.toString());
        }
    }

    public void listFile(String rp, String modifyTag){
        File file=new File(rp);
        File list[]=file.listFiles();
        for(int i=0;i<list.length;i++) {
            try {
                if (list[i].isDirectory()) {
                    new traverseDir().listFile(list[i].toString(), modifyTag);
                }
                else {
                    if(isJavaFile(list[i].toString())) {
//                        replace(modifyTag, list[i].toString());                //read a file and do our work here.
                    }

                }
            } catch (Exception ex) {
                ex.printStackTrace();
                System.out.println("Access deny"+list[i].getAbsolutePath());
            }
        }
    }

    public void replace(String strReplacement, String filePath) throws FileNotFoundException, UnsupportedEncodingException {
        File file = new File(filePath);
        file.setWritable(true);

        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF-8"));
        StringBuffer strBuf = new StringBuffer();

        try {
            String line = null;

            while((line = br.readLine()) != null) {
                //System.out.println(line);
                //import com.android.google.R.
                Pattern pattern = Pattern.compile("^[ ]*import//scom.android.google.R[//s]*;[//s]*$");
                Matcher m = pattern.matcher(line);
                if(m.find()) {
                    //System.out.println("found: " + line);
                    line = "import com.android.google.R."+strReplacement+".R;";    //  replace the found line here.
                }

                strBuf.append(line+"/r/n");
            }

            br.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        FileOutputStream wf = new FileOutputStream(file);
        try {
            wf.write(strBuf.toString().getBytes());
        } catch(IOException e) {
            e.printStackTrace();
        }

    }

    public boolean isJavaFile(String filePath) {
        if(filePath.trim().endsWith(".java")) {
            return true;
        }
        return false;
    }

}