public void addContext(String str){
  if (str == null) {
    throw new NullPointerException("str == null");
  }
  context.append(str);
  if (!str.endsWith("\n")) {
    context.append('\n');
  }
}

public void addContext ( String str ) { if ( str == null ) { throw new NullPointerException ( "str == null" ) ; } context . append ( str ) ; if ( ! str . endsWith ( "\n" ) ) { context . append ( '\n' ) ; } }
adds a line of context to this instance .
