Java Lambda: bug or feature with Predicate

Question

I attempted to make a multiple line Predicate by first adding curly brackets but Eclipse complains about the following code:

Stream<String> stringStream = temp.flatMap(x -> Arrays.stream(x));
Stream<String> stream = stringStream.filter(x -> {"a".equals(x.toString());});

It says after placing a red line under filter: "The method filter(Predicate<? super String>) in the type Stream<String> is not applicable for the arguments ((<no type> x) -> {})"

Is this because multiline predicates are not allowed or am I making some other mistake?

Answer 1

If you use brackets, you need to include the return keyword. If it is a single expression you can omit both the brackets and the return keyword.

Answer 2

The {} make a small block of code. So you need to return true or false int the predicate.

Stream<String> stream = stringStream.filter(x -> {return "a".equals(x.toString());});

Answer 3

Either do this,

Stream<String> stream = stringStream.filter(x -> "a".equals(x.toString()));

or add the return

Stream<String> stream = stringStream.filter(x -> {return "a".equals(x.toString());});