Please help me to understand how to replace lambdas with method reference for the method below.
public List<Person> sortByStartDate_ASC(LinkedHashSet<Person> personList) {
List<Person> pList = new ArrayList<Person>(personList);
Collections.sort(pList, (Person person1, Person person2) -> person1
.getStartDate().compareTo(person2.getStartDate()));
return pList;
}
The equivalent method reference would be comparing(Person::getStartDate)
- note that in your specific case you could sort the stream directly. Also there is no point restricting your method to only accept LinkedHashSet
s - any collection would do:
public List<Person> sortByStartDate_ASC(Collection<Person> personList) {
return personList.stream()
.sorted(comparing(Person::getStartDate))
.collect(toList());
}
Note required static imports:
import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.toList;
使用Comparator.comparing
帮助方法:
Collections.sort(pList, Comparator.comparing(Person::getStartDate));
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