Question

I want to apply a function to a collection, map, etc, using Guava.

Basically, I need to resize the rows and columns of a Table separately so all rows and columns are of equal size, doing something like this:

    Table<Integer, Integer, Cell> table = HashBasedTable.create();
    Maps.transformValues(table.columnMap(), new ResizeFunction(BlockDimension.WIDTH));
    Maps.transformValues(table.rowMap(), new ResizeFunction(BlockDimension.HEIGHT));

public interface Cell {
    int getSize(BlockDimension dimension);
    void setSize(BlockDimension dimension);
}

I already have an idea of what the ResizeFunction should be. However, I need to apply it, not just return a Collection.

Answer 1

In Guava, you don’t convert existing Lists, but instead create a new one using Iterables.transform:

final List<String> list = Arrays.asList("race", "box");
final List<String> transformed =
    Lists.newArrayList(Iterables.transform(list, new Function<String, String>() {

        @Override
        public String apply(final String input) {
            return new StringBuilder().append(input).append("car").toString();
        }
    }));
System.out.println(transformed);

Output:

[racecar, boxcar]

Or, if you don’t need a List and a Collection will do, you can use a transformed live view:

final Collection<String> transformed =
    Collections2.transform(list, new Function<String, String>() {

        @Override
        public String apply(final String input) {
            return new StringBuilder().append(input).append("car").toString();
        }
    });

This Collection is a live view of the underlying one, so changes to list will be reflected in this Collection.