Question: I'd like to convert the following code, which breaks from the outer loop, into Java 8 `Stream`s.

```
private CPBTuple getTuple(Collection<ConsignmentAlert>  alertsOnCpdDay)
{
    CPBTuple cpbTuple=null;

    OUTER:
    for (ConsignmentAlert consignmentAlert : alertsOnCpdDay) {
        List<AlertAction> alertActions = consignmentAlert.getAlertActions();
        for (AlertAction alertAction : alertActions) {
            cpbTuple = handleAlertAction(reportDTO, consignmentId, alertAction);
            if (cpbTuple.isPresent()) {
                break OUTER;
            }
        }
    }
    return cpbTuple;
}

```

Answer: 
Something along the lines of this should suffice:

```
return alertsOnCpdDay.stream()
              .flatMap(s-> s.getAlertActions().stream())
              .map(s-> handleAlertAction(reportDTO, consignmentId, s))
              .filter(s-> s.isPresent())
              .findFirst().orElse(null);

```

That said, a better option would be to change the method return type to `Optional<CPBTuple>` and then simply return the result of `findFirst()`. e.g.

```
private Optional<CPBTuple> getTuple(Collection<ConsignmentAlert> alertsOnCpdDay) {
    return alertsOnCpdDay.stream()
                  .flatMap(s-> s.getAlertActions().stream())
                  .map(s-> handleAlertAction(reportDTO, consignmentId, s))
                  .filter(s-> s.isPresent())
                  .findFirst();
}

```

This is better because it better documents the method and helps prevent the issues that arise when dealing with nullity.
Every answer here uses `flatMap`, which until java-10 [is not lazy](https://stackoverflow.com/questions/46288915/is-flatmap-guaranteed-to-be-lazy). In your case that would mean that `alertActions` is traversed entirely, while in the for loop example - not. Here is a simplified example:

```
static class User {
    private final List<String> nickNames;

    public User(List<String> nickNames) {
        this.nickNames = nickNames;
    }

    public List<String> getNickNames() {
        return nickNames;
    }
}

```

And some usage:

```
public static void main(String[] args) {
    Arrays.asList(new User(Arrays.asList("one", "uno")))
            .stream()
            .flatMap(x -> x.getNickNames().stream())
            .peek(System.out::println)
            .filter(x -> x.equalsIgnoreCase("one"))
            .findFirst()
            .get();
}

```

In `java-8` this will print *both* `one` and `uno`, since `flatMap` is not lazy.

On the other hand in `java-10` this will print `one` - and this is what you care about if you want to have your example translated to `stream-based` 1 to 1.