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Starts from java 8 to iterate throug list I can use both:

List list = new ArrayList(); 1. list.forEach(...) 2. list.stream().forEach(...)

Is it any advantages of using second case? To convert list to stream?

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There are no advantages of using the second case, unless you have a parallel stream. There is a disadvantage, namely that Stream.forEach() doesn't guarantee to respect encounter order. A more accurate (but still unnecessary) equivalent would be Stream.forEachOrdered().

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Does the non-guarantee of encounter order of forEach also apply to non parallel streams that have ordered source?
@tsolakp Briefly, yes. See here for more: stackoverflow.com/q/34247318/1553851
Someone got to write better Javadoc:). Here is snippet from Javadoc as well. "If a stream is ordered, repeated execution of identical stream pipelines on an identical source will produce an identical result;"
@shmosel plus one, I just did not find the right words that even if forEach operates only via side-effects, adding elements to a list via stream().forEach is strongly discouraged and it might produce wrong results, while the other one would be ok.
@Eugene OP never mentioned such a use. As for side-effects in general, I'll just quote the docs: A small number of stream operations, such as forEach() and peek(), can operate only via side-effects; these should be used with care.
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No, in theory, the second option is worse than the first one - you pay the cost of instantiation/garbage-collection and calling a Stream instance and don't really get any benefit in return.

Additionally, in theory the iteration order of Stream.forEach() isn't deterministic.

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