Java8 Stream - use filter collect foreach in single line

Question

Is't possible to use filter(),collect() and foreach() in single statement instead of multiple statements?

I have a map and need to filter based on some condition and set some values to the content and return the map. My current looks like below, but i want all 3 in single statement.

Map inputMap (contains all info)

Map<String, Person> returnMap; 
            returnMap = map.entrySet().stream()
            .filter(p ->  p.getValue().getCourse() == 123)
            .collect(Collectors.toMap(p -> p.getKey(), p -> p.getValue()));

            returnMap.entrySet().stream().forEach((entry) -> {
                Person person= entry.getValue();                
                person.setAction("update");
                person.setLastUpdatedTime(new Date());
            });

can this be converted to,

  Map<String, Person> returnMap; 
                returnMap = map.entrySet().stream()
                .filter(p ->  p.getValue().getCourse() == 123)
                .collect(Collectors.toMap(p -> p.getKey(), p -> p.getValue())) 
 .forEach((entry) -> {
                    Person person= entry.getValue();                
                    person.setAction("update");
                    person.setLastUpdatedTime(new Date());
                });

(this code doesn't work)

Answer 1

The problem is that forEach does not return an object so you have to handle it different. You can do it this way:

Map<String, Person> returnMap = new HashMap<>(); 
map.entrySet().stream()
              .filter(p ->  p.getValue().getCourse() == 123)
              .forEach((entry) -> {
                    Person person = entry.getValue();                
                    person.setAction("update");
                    person.setLastUpdatedTime(new Date());
                    returnMap.put(entry.getKey(), person);
                });

Answer 2

There is no sense in insisting on doing it with one operation. Regardless of how you write it down, these are two operations.

But one thing you should consider, is, that there are more ways than entrySet().stream() to process all elements:

Map<String, Person> returnMap = map.entrySet().stream()
    .filter(p ->  p.getValue().getCourse() == 123)
    .collect(Collectors.toMap(p -> p.getKey(), p -> p.getValue()));

returnMap.values().forEach(person -> {          
    person.setAction("update");
    person.setLastUpdatedTime(new Date());
});

If you still insist on making it look like a single operation, you can do it this way:

Map<String, Person> returnMap = map.entrySet().stream()
    .filter(p ->  p.getValue().getCourse() == 123)
    .collect(Collectors.collectingAndThen(
        Collectors.toMap(p -> p.getKey(), p -> p.getValue()),
        tmp -> {
            tmp.values().forEach(person -> {          
                person.setAction("update");
                person.setLastUpdatedTime(new Date());
            });
            return tmp;
        })
    );

This is syntactically a single statement, still, it does exactly the same as the former variant.