Understanding Spliterator, Collector and Stream in Java 8

Question

I am having trouble understanding the Stream interface in Java 8, especially where it has to do with the Spliterator and Collector interfaces. My problem is that I simply ca

Answer 1

The following are examples of using the predefined collectors to perform common mutable reduction tasks:

 // Accumulate names into a List
 List list = people.stream().map(Person::getName).collect(Collectors.toList());

 // Accumulate names into a TreeSet
 Set set = people.stream().map(Person::getName).collect(Collectors.toCollection(TreeSet::new));

 // Convert elements to strings and concatenate them, separated by commas
 String joined = things.stream()
                       .map(Object::toString)
                       .collect(Collectors.joining(", "));

 // Compute sum of salaries of employee
 int total = employees.stream()
                      .collect(Collectors.summingInt(Employee::getSalary)));

 // Group employees by department
 Map> byDept
     = employees.stream()
                .collect(Collectors.groupingBy(Employee::getDepartment));

 // Compute sum of salaries by department
 Map totalByDept
     = employees.stream()
                .collect(Collectors.groupingBy(Employee::getDepartment,
                                               Collectors.summingInt(Employee::getSalary)));

 // Partition students into passing and failing
 Map> passingFailing =
     students.stream()
             .collect(Collectors.partitioningBy(s -> s.getGrade() >= PASS_THRESHOLD));