code: public String next( int n ) {
        int i = this.myIndex;
        int j = i + n;
        if( j >= this.mySource.length() ){
           throw syntaxError( "Substring bounds error" );
        }
        this.myIndex += n;
        return this.mySource.substring( i, j );
     }
docs: Get the next n characters.
  
  @param n The number of characters to take.
  @return A string of n characters.
  @throws JSONException Substring bounds error if there are not n characters
  remaining in the source string.