How convert string of separate words to separate elements of list by using stream api

Question

Try to studying Stream API. So, I have a list of strings like this:

118.111.97.113
119.122.122.122
122.122.122.97
122.122.122.99
122.122.122.100

I need to split it by '.' and separate numbers put as separate value to new collection. Like this:

I know about flatMap method, that can assume one value and return several, but how use it correctly, have no one idea. Can you help me or give some ideas?

Thanks!

think of flatMap as squeezing a fruit with seeds, you get one fruit as input and lots of seeds as output — Eugene
– Eugene, Commented Jul 16, 2018 at 14:16

azro · Accepted Answer · 2018-07-16 14:08:22Z

5

You may do

List<String> initial;
List<String> all = initial.stream().flatMap(str -> Arrays.stream(str.split("\\.")))
                                   .collect(Collectors.toList());

answered Jul 16, 2018 at 14:08

azro

54.2k9 gold badges38 silver badges75 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Holger Over a year ago

@Eugene "\\." is a single character delimiter for which String.split will not create a Pattern at all.

Eugene Over a year ago

@Holger isn't that an internal detail? :)

Holger Over a year ago

@Eugene Not different to assuming that creating a Pattern each time is expensive or that there is no Pattern cache behind String.split. Sometimes, when you have to make a choice between two equivalent variants, you have to consider what is reasonable to expect from implementations and what the common implementation(s) actually do…

azro Over a year ago

@Eugene I did some quick test, list ok 100k elem, 50iterations, and it's not quicker at all to build the pattern before, even sometimes it's slower

Eugene Over a year ago

@azro then this is a problem of some warm-up I guess, not an indication of which is slower/faster

Eugene · Accepted Answer · 2018-07-16 14:14:43Z

5

Something alone the lines of:

Pattern p = Pattern.compile("\\.");
yourStreamOfStrings.flatMap(p::splitAsStream)
            .collect(Collectors.toList());

answered Jul 16, 2018 at 14:14

Eugene

122k17 gold badges219 silver badges335 bronze badges

Collectives™ on Stack Overflow

How convert string of separate words to separate elements of list by using stream api

2 Answers 2

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related