question: public void add ( int position , int height ) { int currHeight = mMap . get ( position , - 1 ) ; if ( currHeight != height ) { if ( currHeight == - 1 ) { if ( mMap . size ( ) == mMaxSize ) { mMap . delete ( mOrder . remove ( 0 ) ) ; } } else { mOrder . remove ( ( Integer ) position ) ; } mMap . put ( position , height ) ; mOrder . add ( position ) ; } }
target:  Add item height at position if doesn't already exist.