question: public void doHistory ( KeyEvent e ) { if ( e . getSource ( ) == m_Input ) { switch ( e . getKeyCode ( ) ) { case KeyEvent . VK_UP : if ( m_HistoryPos > 0 ) { m_HistoryPos -- ; String command = m_CommandHistory . elementAt ( m_HistoryPos ) ; m_Input . setText ( command ) ; } break ; case KeyEvent . VK_DOWN : if ( m_HistoryPos < m_CommandHistory . size ( ) ) { m_HistoryPos ++ ; String command = "" ; if ( m_HistoryPos < m_CommandHistory . size ( ) ) { command = m_CommandHistory . elementAt ( m_HistoryPos ) ; } m_Input . setText ( command ) ; } break ; default : break ; } } }
target:  Changes the currently displayed command line when certain keys are pressed. The up arrow moves back through history entries and the down arrow moves forward through history entries.