question: private void revalidateAxisExtrema ( ) { synchronized ( this ) { for ( Entry < DataSource , Map < Integer , String > > entryByDataSource : columnToAxisMappingByDataSource . entrySet ( ) ) { DataSource dataSource = entryByDataSource . getKey ( ) ; Map < Integer , String > columnToAxisMapping = entryByDataSource . getValue ( ) ; for ( Entry < Integer , String > entry : columnToAxisMapping . entrySet ( ) ) { Integer colIndex = entry . getKey ( ) ; String axisName = entry . getValue ( ) ; Column < ? > col = dataSource . getColumn ( colIndex ) ; Double min = axisMin . get ( axisName ) ; Double max = axisMax . get ( axisName ) ; if ( min == null || max == null ) { min = col . getStatistics ( Statistics . MIN ) ; max = col . getStatistics ( Statistics . MAX ) ; } else { min = Math . min ( min , col . getStatistics ( Statistics . MIN ) ) ; max = Math . max ( max , col . getStatistics ( Statistics . MAX ) ) ; } axisMin . put ( axisName , min ) ; axisMax . put ( axisName , max ) ; } } } }
target:  Rebuilds cached plot data.