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  1. import java.util.List;
  2. import java.util.Map;
  3. import java.util.Set;
  4. import java.util.function.Function;
  5. import java.util.stream.Collectors;
  6.  
  7. class Department {
  8. 	String deptId;
  9.  
  10. 	public Department(String deptId) {
  11. 		this.deptId = deptId;
  12. 	}
  13.  
  14. 	public String getDeptId() {
  15. 		return deptId;
  16. 	}
  17.  
  18. 	@Override
  19. 	public String toString() {
  20. 		return "Department [deptId=" + deptId + "]";
  21. 	}
  22. }
  23.  
  24. class Employee {
  25. 	String empId;
  26. 	List<Department> departments;
  27.  
  28. 	public Employee(String empId, List<Department> departments) {
  29. 		this.empId = empId;
  30. 		this.departments = departments;
  31. 	}
  32.  
  33. 	public String getEmpId() {
  34. 		return empId;
  35. 	}
  36.  
  37. 	public List<Department> getDepartments() {
  38. 		return departments;
  39. 	}
  40.  
  41. 	@Override
  42. 	public String toString() {
  43. 		return "Employee [empId=" + empId + ", departments=" + departments + "]";
  44. 	}
  45. }
  46.  
  47. public class Main {
  48. 	public static void main(String[] args) {
  49. 		Department a = new Department("a");
  50. 		Department b = new Department("b");
  51. 		Department c = new Department("c");
  52.  
  53. 		Employee e1 = new Employee("e1", List.of(a, b));
  54. 		Employee e2 = new Employee("e2", List.of(c, b));
  55. 		Employee e3 = new Employee("e3", List.of(c, a));
  56. 		Employee e4 = new Employee("e4", List.of(a, b, c));
  57.  
  58. 		List<Employee> employees = List.of(e1, e2, e3, e4);
  59. 		Set<Department> departments = employees.stream().flatMap(employee -> employee.getDepartments().stream())
  60. 				.collect(Collectors.toSet());
  61.  
  62. 		Map<Department, List<Employee>> map = 
  63. 				departments.stream()
  64. 							.collect(Collectors.toMap(
  65. 										Function.identity(),
  66. 										d -> employees.stream().filter(e -> e.getDepartments().contains(d)).collect(Collectors.toList())
  67. 									)
  68. 							);
  69.  
  70. 		map.entrySet().forEach(System.out::println);
  71. 	}
  72. }
Success #stdin #stdout 0.19s 53904KB
comments (?)
stdin 
Standard input is empty
stdout 
Department [deptId=c]=[Employee [empId=e2, departments=[Department [deptId=c], Department [deptId=b]]], Employee [empId=e3, departments=[Department [deptId=c], Department [deptId=a]]], Employee [empId=e4, departments=[Department [deptId=a], Department [deptId=b], Department [deptId=c]]]]
Department [deptId=a]=[Employee [empId=e1, departments=[Department [deptId=a], Department [deptId=b]]], Employee [empId=e3, departments=[Department [deptId=c], Department [deptId=a]]], Employee [empId=e4, departments=[Department [deptId=a], Department [deptId=b], Department [deptId=c]]]]
Department [deptId=b]=[Employee [empId=e1, departments=[Department [deptId=a], Department [deptId=b]]], Employee [empId=e2, departments=[Department [deptId=c], Department [deptId=b]]], Employee [empId=e4, departments=[Department [deptId=a], Department [deptId=b], Department [deptId=c]]]]
https://ideone.com/g1lKPX
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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