Null safe Collection as Stream in Java 8

Question

I am looking for method that can make stream of collection, but is null safe. If collection is null, empty stream is returned. Like this:

Utils.nullSafeStream(collection).filter(...); 

I have created my own method:

public static <T> Stream<T> nullSafeStream(Collection<T> collection) {     if (collection == null) {         return Stream.empty();     }     return collection.stream(); } 

But I am curious, if there is something like this in standard JDK?

Answer 1

You could use Optional :

Optional.ofNullable(collection).orElse(Collections.emptySet()).stream()... 

I chose Collections.emptySet() arbitrarily as the default value in case collection is null. This will result in the stream() method call producing an empty Stream if collection is null.

Example :

Collection<Integer> collection = Arrays.asList (1,2,3); System.out.println (Optional.ofNullable(collection).orElse(Collections.emptySet()).stream().count ()); collection = null; System.out.println (Optional.ofNullable(collection).orElse(Collections.emptySet()).stream().count ()); 

Output:

3 0 

Alternately, as marstran suggested, you can use:

Optional.ofNullable(collection).map(Collection::stream).orElse(Stream.empty ())...