public void pageUp() {
    if (currentPosition > 0) {
      int previousPosition = currentPosition;
      currentPosition = 0;
      showMode(previousPosition);
      showMode(currentPosition);
      modeScreenView.refreshTerminal();
    }
  }
The presentation logic for the mode screen.
hbase-hbtop/src/main/java/org/apache/hadoop/hbase/hbtop/screen/mode/ModeScreenPresenter.java