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  1. import java.util.List;
  2.  
  3. class Ideone {
  4. 	public static void main (String[] args) {
  5. 		List students = List.of(
  6. 				Student.of(1.0),
  7. 				"foo",
  8. 				Student.of(2.0),
  9. 				new Object(),
  10. 				Student.of(3.0),
  11. 				Student.of(4.0));
  12.  
  13. 		System.out.println(sumScore(students));
  14. 	}
  15.  
  16. 	public static double sumScore(List students) {
  17. 		return ((List<?>) students).stream()
  18. 			.filter(o -> o instanceof Student)
  19. 			.map(o -> (Student) o)
  20. 			.mapToDouble(Student::getScore)
  21. 			.sum();
  22. 	}
  23. }
  24.  
  25. class Student {
  26. 	final double score;
  27.  
  28. 	private Student(double score) {
  29. 		this.score = score;
  30. 	}
  31.  
  32. 	public static Student of(double score) {
  33. 		return new Student(score);
  34. 	}
  35.  
  36. 	public double getScore() {
  37. 		return score;
  38. 	}
  39. }
Success #stdin #stdout 0.08s 34316KB
comments (?)
stdin 
Standard input is empty
stdout 
10.0
https://ideone.com/2PYa3U
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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