I need to get the data back similar to flatMap but it is not working in some scenario. Following are the details. Below is the pseudo code
class Employee { String name; int age; } Employee emp1 = new Employee("Peter",30); Employee emp2 = new Employee("Bob",25); Set<Employee> empSet1 = new HashSet(); empSet1.add(emp1); empSet1.add(emp2); Employee emp3 = new Employee("Jack",31); Employee emp4 = new Employee("Laura",27); Set<Employee> empSet2 = new HashSet(); empSet2.add(emp3); empSet2.add(emp4); Map<String,Set<Employee>> empLocationMap = new HashMap(); empLocationMap.put("location1",empSet1); empLocationMap.put("location2",empSet2); Set<Employee> empSet = getEmployeeSetForLocation("location1",empLocationMap); private static Set getEmployeeSetForLocation(String location,Map<String,Set<Employee>> locationEmpMap) { Object filteredObject = locationMap.entrySet().stream().filter(element-> element.getKey().equals(location)).flatMap(element-> Stream.of(element)).collect(Collectors.toSet()); return new HashSet(filteredObject ); }
The filteredObject in the method getEmployeeSetForLocation on inspection shows containing 1 element and that element is of type Set containing 2 elements. I want to know, what modification can I make in the above logic to flatten the structure further so that filteredObject shows a set with 2 elements. Any pointers will be helpful. I am using Java 8.
Regards
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Answer
Use flatMap, mapping the stream of MapEntry
to stream of Employee
Set<Employee> filteredObject = locationMap.entrySet().stream() -- Here you have stream of Map.Entry, where value is employee .filter(element -> element.getKey().equals(location)) -- And here is how to convert this stream to Stream<Employee> .flatMap(s -> s.getValue().stream()) .collect(Collectors.toSet());