How to get the String representation of all elements in a Java 8 stream

Question

Using Eclipse and Java -version 1.8

I have this code:

    public Stream<Ship> remainingShips() {
        return this.b.getShips().stream().filter(s -> !s.isSunk());.
    }

    public Stream<Ship> sunkShips() {
        return this.b.getShips().stream().filter(s -> s.isSunk());.
    }

I want to print out all the items in the stream, by calling

System.out.println("Sunk ships => " + this.opponent.sunkShips());

but this will just print the stream object, how can I get access to all the items in stream and print each out?

Can you come up with better title for this question? Something like, "How to print all elements in stream?". Thanks — OlegTheCat
– OlegTheCat, Commented Sep 19, 2016 at 8:19

Eran · Accepted Answer · 2016-09-19 05:22:08Z

6

You can iterate over the elements of the Stream and print them :

System.out.println("Sunk ships => ");
this.opponent.sunkShips().forEach(System.out::println);

Or you can generate a List from the Stream and print it :

System.out.println("Sunk ships => " + this.opponent.sunkShips().collect(Collectors.toList());

answered Sep 19, 2016 at 5:22

Eran

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3 Comments

Alexander Mills Over a year ago

thanks! what if I want to print the stream only if the stream has more than 0 items? is there a good way to do that with streams/filters in Java?

Eran Over a year ago

@AlexMills In order to find if a Stream is empty, you have to use some terminal operation (such as findAny() or findFirst(), which will close the Stream. Therefore I suggest you produce a List (List<Ship> ships = this.opponent.sunkShips().collect(Collectors.toList();) and print it if it's not empty.

Holger Over a year ago

There is no point in collecting into a List when you already know that you are only interested in a String representation. You can use, e.g. .map(Object::toString).collect(Collectors.joining(", "))…

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