This example will show how to filter a list of objects by field in a class using groovy. The set is a class Currency and we will initialize a collection creating three elements. Next calling the findAll() method we will pass a closure that filter the list by checking if the amount is greater than 1.03. The result is 2 elements. The second snippet will demonstrate how to reduce the list and only return even numbers. A related example of show how to filter elements in a list using java 8.
Setup
@ToString
class Currency {
def amount
def year
def country
}Filter list by field
@Test
void filter_object_by_field () {
def currencyCollection = [new Currency(amount: 1.04, year: 1998, country: "US"),
new Currency(amount: 1.02, year: 2001, country: "US"),
new Currency(amount: 1.07, year: 2005, country: "EU")]
def filteredList = currencyCollection.findAll({p -> p.amount > 1.03})
print(filteredList)
assert 2 == filteredList.size()
}Output
[com.levelup.groovy.collections.FilterCollection$Currency(1.04, 1998, US), com.levelup.groovy.collections.FilterCollection$Currency(1.07, 2005, EU)]Filter even numbers
@Test
void filter_even_numbers() {
def numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
def evenNumbers = numbers.findAll({ it % 2 == 0 })
assert [2, 4, 6, 8] == evenNumbers
}