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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6. import java.util.stream.Collectors;
  7. import java.util.function.Function;
  8.  
  9. /* Name of the class has to be "Main" only if the class is public. */
  10. class Ideone
  11. {
  12. 	public static void main (String[] args) throws java.lang.Exception
  13. 	{
  14. 		final Collection<Record> records = new ArrayList<>();
  15. 		records.add(new Record("11111", "Orlando"));
  16. 		records.add(new Record("11111", "Orlando"));
  17. 		records.add(new Record("11111", "Orlando"));
  18. 		records.add(new Record("11111", "Los Angeles"));
  19. 		records.add(new Record("11111", "Los Angeles"));
  20. 		records.add(new Record("11111", "San Francisco"));
  21.  
  22. 		records.add(new Record("22222", "Cincinatti"));
  23. 		records.add(new Record("22222", "Cleveland"));
  24. 		records.add(new Record("22222", "Cleveland"));
  25. 		records.add(new Record("22222", "Columbus"));
  26. 		records.add(new Record("22222", "Columbus"));
  27. 		records.add(new Record("22222", "Columbus"));
  28.  
  29. 		final Map<String, List<Record>> recordsByZip = records.stream()
  30. 		    .collect(Collectors.groupingBy(Record::getZip));
  31.  
  32. 		recordsByZip.forEach((zip, entries) -> {
  33. 			final Map<String, Long> frequencyMap = entries.stream()
  34. 				.map(Record::getCity)
  35. 				.collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
  36.  
  37. 			System.out.println("Frequency map for zip " + zip);
  38. 			frequencyMap.forEach((city, frequency) -> System.out.println(city + ": " + frequency));
  39. 			System.out.println();
  40. 		});
  41. 	}
  42. }
  43.  
  44. class Record {
  45. 	private String zip;
  46. 	private String city;
  47.  
  48. 	public Record(String zip, String city) {
  49. 		this.zip = zip;
  50. 		this.city = city;
  51. 	}
  52.  
  53. 	public String getZip() {
  54. 		return zip;
  55. 	}
  56. 	public void setZip(String zip) {
  57. 		this.zip = zip;
  58. 	}
  59. 	public String getCity() {
  60. 		return city;
  61. 	}
  62. 	public void setCity(String city) {
  63. 		this.city = city;
  64. 	}
  65. }
Success #stdin #stdout 0.1s 711680KB
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Standard input is empty
stdout
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Frequency map for zip 11111
San Francisco: 1
Orlando: 3
Los Angeles: 2

Frequency map for zip 22222
Cincinatti: 1
Columbus: 3
Cleveland: 2
https://ideone.com/IhL5te
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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