Integer from String via Lambda expression

Question

I have a small problem, namely I want to get Integer from a String via lambda expression. I wrote small code but i get only single chars.

Example:

String = "He11o W00rld"

I get [1, 1, 0, 0] but I want [11, 00]. Is there any solution for this?

My code:

Function<String, List<Integer>> collectInts = f -> { 
    return f.chars()
            .filter( s -> (s > 47 && s < 58))
            .map(r -> r - 48)
            .boxed()
            .collect(Collectors.toList());};

Any particular reason you need to do it by lambda expression? — Joachim Isaksson
– Joachim Isaksson, Commented Apr 8, 2016 at 17:47

Alex Salauyou · Accepted Answer · 2016-04-08 18:05:17Z

4

You may use the following lambda:

Function<String, List<Integer>> collectInts = s ->
   Pattern.compile("[^0-9]+")
          .splitAsStream(s)
          .filter(p -> !p.isEmpty())
          .map(Integer::parseInt)
          .collect(Collectors.toList());

Here is used Pattern.splitAsStream() stream generator, which splits a given input by regex. Then each part is checked if it is not empty and converted to Integer.

Besides, if you need 00 instead of 0, you should not parse a number (skip Integer::parseInt mapping and collect to List<String>).

edited Apr 8, 2016 at 18:05

answered Apr 8, 2016 at 17:59

Alex Salauyou

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Comments

Jean Logeart · Accepted Answer · 2016-04-08 18:00:01Z

2

You can do:

Stream.of(f.split("[^\\d]+"))
  .filter(s -> !s.isEmpty())  // because of the split function
  .map(Integer::parseInt)
  .collect(toList())

answered Apr 8, 2016 at 18:00

Jean Logeart

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