How to call multiple terminal operation on a Java stream

Question

I know that whenever we call any terminal method on a stream, it gets closed.

If we try to call any other terminal function on a closed stream it will result in a java.lang.IllegalStateException: stream has already been operated upon or closed.

However, what if we want to reuse the same stream more than once?

How to accomplish this?

Answer 1

Yes its a big NO in Java 8 streams to reuse a stream

For example for any terminal operation the stream closes when the operation is closed. But when we use the Stream in a chain, we could avoid this exception:

Normal terminal operation:

Stream<String> stream =
    Stream.of("d2", "a2", "b1", "b3", "c")
        .filter(s -> s.startsWith("a"));

stream.anyMatch(s -> true);    // ok
stream.noneMatch(s -> true);   // exception

But instead of this, if we use:

Supplier<Stream<String>> streamSupplier =
    () -> Stream.of("d2", "a2", "b1", "b3", "c")
            .filter(s -> s.startsWith("a"));

streamSupplier.get().anyMatch(s -> true);   // ok
streamSupplier.get().noneMatch(s -> true);  // ok

Here the .get() "constructs" a new stream and NOT reuse whenever it hits this point.

Cheers!