Pure Functions

public int addNumbers(int a, int b) {
    return a + b;
}

public int countUnique(List<String> names) {
    Set<String> nameSet = new HashSet<>(names);
    return nameSet.size();
}

public List<String> filterANames(List<String> names) {
    List<String> result = new ArrayList<>();
    for(String name : names) {
        if(name.startsWith("A")) {
            result.add(name);
        }
    }
    return result;
}