output: #fixed code
                                  public OutputStream writeInteger(int value) throws IOException {
          writeInteger(value, 8);
          return this;
      }
input: #vulnerable code 
                                  public OutputStream writeInteger(int value) throws IOException {
          write(getIsoBytes(String.valueOf(value)));
          return this;
      } 
                              #location 2 
                              #vulnerability type NULL_DEREFERENCE