如何在Java中更新数据框的所有列

Question

In scala we can update all the columns of a dataframe with the help of below

val outputDF = InputDF.select(InputDF.columns.map(c => toLower(col(c))):_*)

How to handle the above scenario in Java in an immutable way ?

Answer 1

It would be pretty the same:

inputDF.select(Arrays.stream(inputDF.columns()).map(c ->lower(col(c))).toArray(Column[]::new));

You can also do it with a loop:

    Dataset outputDF = inputDF;
    for (String c : inputDF.columns()){
        outputDF = outputDF.withColumn(c, lower(col(c)));
    }