Get a subset of a map

This example will show how to filter a map by keys creating a submap in groovy. First initializing a map of months then calling map.submap() returning months contained in the first quarter. A comparable example demonstrates how to get a subset of a map in java java, java 8 and guava.

Filter map by key

@Test
void filter_map_by_key() {

    def MONTHS = [
            1: "January",
            2: "February",
            3: "March",
            4: "April",
            5: "May",
            6: "June",
            7: "July",
            8: "August",
            9: "September",
            10: "October",
            11: "November",
            12: "December",
    ]

    assert [1: "January",
            2: "February",
            3: "March"] == MONTHS.subMap([1, 2, 3])
}