Challenge 3: Calling a Terminal Operation Twice on the Same Stream — Possible Solution
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ReuseDemo.java:

import java.util.List;
import java.util.stream.Stream;

public class ReuseDemo {
    public static void main(String[] args) {
        List<String> names = List.of("Alice", "Bob", "Carol");
        Stream<String> s = names.stream();

        s.forEach(System.out::println);   // first terminal operation -- fine
        s.forEach(System.out::println);   // second terminal operation on the SAME stream object
    }
}

Representative runtime exception:

    Alice
    Bob
    Carol
    Exception in thread "main" java.lang.IllegalStateException: stream
    has already been operated upon or closed
        at java.base/java.util.stream.AbstractPipeline.sourceStageSpliterator(...)
        at java.base/java.util.stream.ReferencePipeline$Head.forEach(...)
        at ReuseDemo.main(ReuseDemo.java:9)

Explanation:
The first forEach() successfully consumes the stream `s`, printing
all three names. Once a terminal operation has run, that specific
Stream object is considered spent -- it doesn't reset or become
reusable. Calling forEach() a second time on the exact same `s`
reference throws IllegalStateException, because there's no data left
for it to operate on; the pipeline was already exhausted.

The fix would be to call names.stream() again to get a brand new
Stream instance for the second forEach(), rather than reusing `s`.

WHY THIS WORKS AS AN ANSWER
------------------------------
This reproduces the exact single-use violation the chapter's warn-box
describes -- two terminal operations on one stream object -- and
explains the IllegalStateException in terms of the stream being
"spent" after its first terminal operation, matching the chapter's
own stated behavior.