Spark如何把NA设置为-1

masterDF = masterDF.na.fill(-1)

其它:

也可以在fill中使用Map，其中key是列名，value可以是Int, Long, Float, Double, String, Boolean.

masterDF.na.fill(masterDF.columns.map(_ -> false).toMap)

来自:

https://stackoverflow.com/questions/51073493/spark-dataframe-na-fill-boolean-column-type

* For example, the following replaces null values in column "A" with string "unknown", and
* null values in column "B" with numeric value 1.0.
* {{{
*   df.na.fill(Map(
*     "A" -> "unknown",
*     "B" -> 1.0
*   ))
* }}}

https://stackoverflow.com/questions/44671597/how-to-replace-null-values-with-a-specific-value-in-dataframe-using-spark-in-jav/44671923