How to assign multiple value from HashMap to variables in Java?

February 1, 2022

I have a HashMap and assign key-value pairs to variable as shown below:

Map<UUID, EmployeeDTO> result = employeeService.getEmployees(employeeUuids);

UUID key = result.entrySet().iterator().next().getKey();
EmployeeDTO value = result.entrySet().iterator().next().getValue();

However, I am not sure about what is a proper way to assign multiple values from this HashMap. I thought a loop of course, but for naming variables, maybe there would be a better approaches. Any idea?

map.forEach((k, v) -> {
    UUID key1 = k;
    EmployeeDTO value1 = v;

    //  what about the other values?
    UUID key2 = k;
    EmployeeDTO value2 = v;
});

>Solution :

You cannot create variables without knowing the size of the map, so you need to store the keys and the values in two separate data structures, for example List:

List<UUID> keys = new ArrayList<>();
List<EmployeeDTO> values = new ArrayList<>();
map.forEach((k, v) -> {
    keys.add(k);
    values.add(k);
});

In case the size of the map is known, you can store the entries in a list and assign the corresponding keys and values:

List<Map.Entry<UUID, EmployeeDTO>> entriesList = new ArrayList<>(map.entrySet());

UUID key1 = entriesList.get(0).getKey();
EmployeeDTO value1 = entriesList.get(0).getValue();

UUID key2 = entriesList.get(1).getKey();
EmployeeDTO value2 = entriesList.get(1).getValue();

// etc.

Obviously you need to do that for each key/value. It is theoretically possible to use a loop and some nasty reflection on the object that holds the variables, but this will do way more harm than good.