Using Java 8 stream methods to get a max value

Question

I would like to get the max value out of a list using java 8 stream methods.

The structure is the following:

• I read a csv file and store the data of every

Answer 1

You can achieve it by this way :

• iterate over the Round of the list
• change from Round object to its List hits,
• use flatMap to go from Stream> to Stream
• change from Hits to its prizeAmount field
• get the max if exists
• if no max (like if list empty or else) return -1

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So a solution using Method reference

int maxPrize = arrRoundarrRound.stream()                      // Stream
                               .map(Round::getHits)           // Stream>
                               .flatMap(List::stream)         // Stream
                               .mapToInt(Hit::getPrizeAmount) // IntStream
                               .max()                         // OptionalInt 
                               .orElse(-1);                   // int

With class lambda and map + flatMap in one :

int maxPrize = arrRoundarrRound.stream()    
                               .flatMap(round -> round.getHits().stream())
                               .mapToInt(hits -> hits.getPrizeAmount())
                               .max()                         
                               .orElse(-1);