question: public static void queueColumnLoad ( ICubicWorld world , CubeIO loader , int x , int z , Consumer < Column > runnable ) { QueuedColumn key = new QueuedColumn ( x , z , world ) ; AsyncColumnIOProvider task = columnTasks . get ( key ) ; if ( task == null ) { task = new AsyncColumnIOProvider ( key , loader ) ; task . addCallback ( runnable ) ; columnTasks . put ( key , task ) ; pool . execute ( task ) ; } else { task . addCallback ( runnable ) ; } }
target:  Queue a column load, running the specified callback when the load has finished