fork download
copy 
  1.  
  2. import java.time.LocalDate;
  3. import java.time.chrono.IsoChronology;
  4. import java.util.ArrayList;
  5. import java.util.HashMap;
  6. import java.util.List;
  7. import java.util.Map;
  8.  
  9. import static java.util.stream.Collectors.groupingBy;
  10. import static java.util.stream.Collectors.toList;
  11.  
  12. class Person {
  13.  
  14.     String name;
  15.     LocalDate birthday;
  16.     Sex gender;
  17.     String emailAddress;
  18.  
  19.     Person(String nameArg, LocalDate birthdayArg, Sex genderArg, String emailArg) {
  20.         name = nameArg;
  21.         birthday = birthdayArg;
  22.         gender = genderArg;
  23.         emailAddress = emailArg;
  24.     }
  25.  
  26.     public enum Sex {
  27.         MALE, FEMALE
  28.     }
  29.  
  30.     public void printPerson() {
  31.         System.out.println(name + ", " + this.getAge());
  32.     }
  33.  
  34.     public int getAge() {
  35.         return birthday.until(IsoChronology.INSTANCE.dateNow()).getYears();
  36.     }
  37.  
  38.     public Sex getGender() {
  39.         return gender;
  40.     }
  41.  
  42.     public String getName() {
  43.         return name;
  44.     }
  45.  
  46.     public String getEmailAddress() {
  47.         return emailAddress;
  48.     }
  49. }
  50.  
  51. class JavaLambda {
  52.     private static ArrayList<Person> members = new ArrayList<>();
  53.  
  54.     public static void main(String[] args) throws java.lang.Exception {
  55.  
  56.         members.add(new Person("Fred", IsoChronology.INSTANCE.date(1980, 6, 20), Person.Sex.MALE, "fred@example.com"));
  57.         members.add(new Person("Jane", IsoChronology.INSTANCE.date(1990, 7, 15), Person.Sex.FEMALE, "jane@example.com"));
  58.         members.add(new Person("Mark", IsoChronology.INSTANCE.date(1990, 7, 15), Person.Sex.MALE, "mark@example.com"));
  59.         members.add(new Person("George", IsoChronology.INSTANCE.date(1991, 8, 13), Person.Sex.MALE, "george@example.com"));
  60.         members.add(new Person("Bob", IsoChronology.INSTANCE.date(2000, 9, 12), Person.Sex.MALE, "bob@example.com"));
  61.  
  62. Map<Integer, List<String>> collect = 
  63.             members.stream()
  64.                    .collect(groupingBy(
  65.                            Person::getAge,
  66.                            mapping(Person::getName, toList()))
  67.                    );
  68.         System.out.println(collect);
  69.     }
  70. }
Compilation error #stdin compilation error #stdout 0.28s 320896KB
comments (?)
stdin
copy 
Standard input is empty
compilation info 
Main.java:66: error: cannot find symbol
                           mapping(Person::getName, toList()))
                           ^
  symbol:   method mapping(Person::getName,Collector<Object,CAP#1,List<Object>>)
  location: class JavaLambda
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object from capture of ?
Main.java:66: error: invalid method reference
                           mapping(Person::getName, toList()))
                                   ^
  non-static method getName() cannot be referenced from a static context
Main.java:65: error: invalid method reference
                           Person::getAge,
                           ^
  non-static method getAge() cannot be referenced from a static context
3 errors
stdout
copy 
Standard output is empty
https://ideone.com/wA60vl
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!