code: public static ASTNode getASTNode(CompilationUnit compilationUnit, int startLine, int endLine) throws ASTNodeNotFoundException {
          requireNonNull(compilationUnit, "compilation unit");
  
          ASTNode node = searchASTNode(compilationUnit, startLine, endLine);
          if (node == null) {
              throw new ASTNodeNotFoundException("No ast node found between " + startLine + " and " + endLine + ".");
          }
          return node;
      }
docs: Searchs the first <CODE>ASTNode</CODE> between the specified
  <CODE>startLine</CODE> and <CODE>endLine</CODE>. If the source line
  doesn't contain an <CODE>ASTNode</CODE>, a
  <CODE>ASTNodeNotFoundException</CODE> is thrown.
  
  @param compilationUnit
  the <CODE>CompilationUnit</CODE>, that contains the
  <CODE>ASTNode</CODE>.
  @param startLine
  the starting source line number.
  @param endLine
  the ending source line number.
  @throws ASTNodeNotFoundException
  if no <CODE>ASTNode</CODE> found between the specifed start
  and end line.