java util Optional

Optional.java

	public static void main(String[] args) {
		
		System.out.println(getEmployeeNames(simulateWsResult1()));
		System.out.println(getEmployeeNames(simulateWsResult2()));
		System.out.println(getEmployeeNames(simulateWsResult3()));
		System.out.println(getEmployeeNames(simulateWsResult4()));
	}
	
	static class Result {
		Departement departement;
	}
	
	
	static class Departement{
		List<Employee> employees;
	}
	

	static class Employee{
		String name;
	}
	
	static List<String> getEmployeeNames(Result r){
		
		return
		Optional.ofNullable(r)
			.map(result -> result.departement)
			.map(dept -> dept.employees)
			.map(empList -> empList.stream())
			.map(empStream -> empStream.filter(e -> e.name != null).map(e -> e.name))
			.orElse(Stream.empty())
			.collect(Collectors.toList());
	}
	
	static Result simulateWsResult1() {
		Employee e1 = new Employee();
		e1.name = "Ali";
		Employee e2 = new Employee();
		e2.name = "Muhammad";
		
		
		Departement dept = new Departement();
		dept.employees = Arrays.asList(e1, e2);
		
		Result result = new Result();
		result.departement = dept;
		
		return result;
	}
	
	static Result simulateWsResult2() {
		Employee e1 = new Employee();
		Employee e2 = new Employee();
		
		Departement dept = new Departement();
		dept.employees = Arrays.asList(e1, e2);
		
		Result result = new Result();
		result.departement = dept;
		
		return result;
	}
	
	static Result simulateWsResult3() {
		Departement dept = new Departement();
		
		Result result = new Result();
		result.departement = dept;
		
		return result;
	}
	
	static Result simulateWsResult4() {
		Result result = new Result();
		
		return result;
	}