Determine whether list2 contains objects for all the unique ids of list1 and whether these objects a-CodePudding

I have 2 variable (day and time) and 2 lists of objects (list1 and list2);

ArrayList<Teacher> list1 = new Teacher<>();
list1.add(new Teacher(1, "Mary"));  //Tid, name
list1.add(new Teacher(2, "Anne")); 
....

ArrayList<Session> list2 = new Session<>();
list2.add(new Session(101, 1, "Monday", "2-4pm")); //Sid, Tid, day, time
list2.add(new Session(102, 1, "Tuesday", "2-4pm"));
list2.add(new Session(103, 2, "Monday", "9-11pm"));
....

String day = "Monday"
String time = "9-11am"

I want to check if all the teachers have classes on monday from 9-11am using the Tid and the given day and time)

This is what I tried - using streams

Predicate<Session> dayEquals = s -> s.getDay().equals(day);
Predicate<Session> timeEquals = s -> s.getTime().equals(time);
Predicate<Session> combinedCondition = dayEquals.and(timeEquals);


if (list2.stream().filter(s -> s.getTid() == t -> t.getTid).anyMatch(combinedCondition)) {
          System.out.println("All teachers are occupied");
}

Thanks!

CodePudding user response：

You can use java stream API for this task. Assuming you have appropriate getters in your Teacher and Session class. I don't understand your approach as the combinedCondition is missing but whatever it may be anyMatch shouldn't be used if the condition checks for all teachers of list 1 to be present as per your question. You should use allMatch that checks if all the elements of list 1 match the given predicate.

// get all the teachers' id as set who have session on given day and time

Set<Integer> tidList =list2.stream()
                .filter(session -> (day.equals(session.day)
                        && time.equals(session.time)))
                .map(Session::getTid)
                .collect(Collectors.toSet());


// check if all the teachers from list1 is in the above set.

boolean result = list1.stream()
                .map(Teacher::getId)
                .allMatch(tidList::contains);