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  1.  
  2. import java.util.*;
  3. import java.lang.*;
  4. import java.io.*;
  5. import java.time.*;
  6. import java.time.format.*;
  7.  
  8. class Ideone {
  9.  
  10. 	public static void main (String[] args) throws java.lang.Exception {
  11.  
  12. 		Person youngest;
  13.  
  14. 		// you could do string comparison if you know the timezones are consistent:
  15.  
  16. 		youngest = listOfPersons.stream()
  17. 		    .max(Comparator.comparing(p -> p.dateOfBirth)).get();
  18.  
  19. 		System.out.println("youngest is: " + youngest.name + " " + youngest.dateOfBirth);
  20.  
  21.         // or you could just parse the date, a safer option (choose ISO_INSTANT or ISO_DATE_TIME depending on needs):
  22.  
  23. 		youngest = listOfPersons.stream()
  24. 		    .max(Comparator.comparing(p -> LocalDateTime.parse(p.dateOfBirth, DateTimeFormatter.ISO_DATE_TIME))).get();
  25.  
  26. 		System.out.println("youngest is: " + youngest.name + " " + youngest.dateOfBirth);
  27.  
  28. 	}
  29.  
  30.  
  31. 	//------------------------------------
  32. 	// types from OP:
  33.  
  34. 	static class Person{
  35. 		String name;
  36. 		String id;
  37. 		String dateOfBirth;
  38. 		int salary;
  39. 	}
  40.  
  41. 	static List <Person> listOfPersons;
  42.  
  43.  
  44. 	//------------------------------------
  45. 	// boring example data initialization:
  46.  
  47. 	// make an iso birthdate string given an age (for initializing data)
  48. 	static String fromAge (int years) {
  49. 		//return LocalDateTime.now().minusYears(years).toString();
  50. 		// add zone to emulate OP's input:
  51. 		return LocalDateTime.now().minusYears(years).toString() + 'Z';
  52. 	}
  53.  
  54. 	// make up some data
  55. 	static {
  56. 		listOfPersons = List.of(
  57. 			// fine for example, but i wouldn't init like this in production
  58. 			new Person() {{ name="helga"; dateOfBirth=fromAge(22); }},
  59. 			new Person() {{ name="mortimer"; dateOfBirth=fromAge(48); }},
  60. 			new Person() {{ name="gertrude"; dateOfBirth=fromAge(6); }},
  61. 			new Person() {{ name="jebediah"; dateOfBirth=fromAge(39); }}
  62. 		);
  63. 		listOfPersons.forEach(p -> System.out.println(p.name + ' ' + p.dateOfBirth));
  64. 	}
  65.  
  66.  
  67. }
Success #stdin #stdout 0.21s 55260KB
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Standard input is empty
stdout
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helga 2000-06-23T03:07:26.084850Z
mortimer 1974-06-23T03:07:26.126628Z
gertrude 2016-06-23T03:07:26.126894Z
jebediah 1983-06-23T03:07:26.127948Z
youngest is: gertrude 2016-06-23T03:07:26.126894Z
youngest is: gertrude 2016-06-23T03:07:26.126894Z
https://ideone.com/HNwcwM
language:
Java (HotSpot 12)
created:
1 year ago
visibility:
public

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