import java.io.PrintStream;
import java.io.PrintWriter;

/**
 * Thrown to indicate a fatal problem.
 **/
public class Problem extends RuntimeException
{
  private Throwable cause_ = null;

  /**
   * Create an instance initialized with 'message' that does not have a
   * cause.
   **/
  public Problem(String message)
  {
    super(message);
  }

  /**
   * Create and instance initialized with 'cause' and 'message'.
   **/
  public Problem(Throwable cause, String message)
  {
    super(message);
    cause_ = cause;
  }

  /**
   * Return the cause of this problem, or null.
   **/
  public Throwable getCause()
  {
    return cause_;
  }

  /**
   * Return the message for this problem. If this has a cause, then the
   * return value includes the problem message, newline, cause message.
   **/
  public String getMessage()
  {
    if (cause_ == null) {
      return super.getMessage();
    } else {
      StringBuffer message = new StringBuffer();
      String superMessage = super.getMessage();
      if (superMessage != null) {
        message.append(superMessage);
        message.append(System.getProperty("line.separator"));
      }
      message.append(cause_.getMessage());
      return message.toString();
    }
  }

  /**
   * Equivalent to {@link #printStackTrace(java.io.PrintStream)
   * printStackTrace(System.err)}.
   **/
  public void printStackTrace()
  {
    printStackTrace(System.err);
  }

  /**
   * Print the stack trace to 's'. If this has a cause, then print its
   * message, "Caused by", and the cause stack trace.
   **/
  public void printStackTrace(PrintStream s)
  {
    if (cause_ == null) {
      super.printStackTrace(s);
    } else {
      synchronized (s) {
        s.println(getClass().getName()+": "+super.getMessage());
        s.print("Caused by ");
        cause_.printStackTrace(s);
      }
    }
  }

  /**
   * Print the stack trace to 's'. If this has a cause, then print its
   * message, "Caused by", and the cause stack trace.
   **/
  public void printStackTrace(PrintWriter s)
  {
    if (cause_ == null) {
      super.printStackTrace(s);
    } else {
      synchronized (s) {
        s.println(getClass().getName()+": "+super.getMessage());
        s.print("Caused by ");
        cause_.printStackTrace(s);
      }
    }
  }
}