question: protected void checkParams ( XCreateWindowParams params ) { if ( params == null ) { throw new IllegalArgumentException ( "Window creation parameters are null" ) ; } params . putIfNull ( PARENT_WINDOW , Long . valueOf ( XToolkit . getDefaultRootWindow ( ) ) ) ; params . putIfNull ( BOUNDS , new Rectangle ( DEF_LOCATION , DEF_LOCATION , MIN_SIZE , MIN_SIZE ) ) ; params . putIfNull ( DEPTH , Integer . valueOf ( ( int ) XConstants . CopyFromParent ) ) ; params . putIfNull ( VISUAL , Long . valueOf ( XConstants . CopyFromParent ) ) ; params . putIfNull ( VISUAL_CLASS , Integer . valueOf ( ( int ) XConstants . InputOnly ) ) ; params . putIfNull ( VALUE_MASK , Long . valueOf ( XConstants . CWEventMask ) ) ; Rectangle bounds = ( Rectangle ) params . get ( BOUNDS ) ; bounds . width = Math . max ( MIN_SIZE , bounds . width ) ; bounds . height = Math . max ( MIN_SIZE , bounds . height ) ; Long eventMaskObj = ( Long ) params . get ( EVENT_MASK ) ; long eventMask = eventMaskObj != null ? eventMaskObj . longValue ( ) : 0 ; eventMask |= XConstants . PropertyChangeMask | XConstants . OwnerGrabButtonMask ; params . put ( EVENT_MASK , Long . valueOf ( eventMask ) ) ; }
target:  Verifies that all required parameters are set. If not, sets them to default values. Verifies values of critical parameters, adjust their values when needed.