- a), b)
- of(), without parameters, produces an empty stream
- java.util.Set
- 135
- 42
- 2121
- No, but it extends the functional interface Consumer and can be passed around as such
- None
- 3
- 1.5
- 42,X,a
- Compilation error, because peek() cannot return anything
- 2
- An alternative Optional object
- a
- One
- Any of filter(), map(), and flatMap()
- Any of distinct(), limit(), sorted(), reduce(), and collect()
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