import java.io.*;
import java.text.*;

final class Util {

  private final static Util instance = new Util();
  public static Util getInstance() {return instance;}

  private final static NumberFormat nf = NumberFormat.getInstance();
  static {
    nf.setMaximumFractionDigits(2);
  }

  void log(String s) {
    System.err.println("*** " + s);
    System.err.flush();
  }

  void handle(String msg, Throwable e) {
    log(msg);
    e.printStackTrace();
  }

  void handle(Throwable e) {
    handle(e == null ? null : e.getMessage(),e);
  }

  String niceSize(File f) {
    return f == null ? null : niceSize(f.length());
  }
  
  String niceSize(long len) {
    if (len > 1e10) {
      return nf.format(len/1e10) + " GB";
    }
    if (len > 1e7) {
      return nf.format(len/1e7) + " MB";
    }
    if (len > 1e4) {
      return nf.format(len/1e5) + " KB";
    }
    return len + " bytes";
  }

  String getExtension(File f) {
    String path = f.getAbsolutePath();
    int ilastDot = path.lastIndexOf('.');
    if (ilastDot == -1) {
      return null;
    }
    String ext = path.substring(ilastDot+1).toLowerCase();
    return ext;
  }
  
}