Split String into Map using Java Streams

Question

I want to split the following String and store it into a Map.

String = "key_a:<value_a1>\r\n\r\nkey_b:<value_b1>\r\n\r\nkey_c:<value_c1, value_c2, value_c3>"

The string can have line breaks in between the pairs. A key can have multiple values that are separated by a , and begin with a < and end with a >.

Now this String needs to be converted to a Map<String, List<String>>.

The structure of the map should look like this:

key_a={value_a1}, 
key_b={value_b1}, 
key_c={value_c1, value_c2, value_c3}

I currently only have the logic for splitting apart the different key-value-pairs from each other, but I don't know how to implement the logic that splits the values apart from each other, removes the brackets and maps the attributes.

String strBody = "key_a:<value_a1>\r\n\r\nkey_b:<value_b1>\r\n\r\nkey_c:<value_c1, value_c2, value_c3>"

Map<String, List<String>> map = Pattern.compile("\\r?\\n")
            .splitAsStream(strBody)
            .map(s -> s.split(":"))
               //...logic for splitting values apart from each other, removing <> brackets and storing it in the map           
            )

Ryuzaki L · Accepted Answer · 2021-04-21 20:40:32Z

2

You can filter the arrays having two values and then use Collectors.groupingBy to group the elements into Map, You can find more examples here about groupingBy and `mapping

 Map<String, List<String>> map = Pattern.compile("\\r?\\n")
            .splitAsStream(strBody)
            .map(s -> s.split(":"))
            .filter(arr -> arr.length == 2)
            .collect(Collectors.groupingBy(arr -> arr[0],
                    Collectors.mapping(arr -> arr[1].replaceAll("[<>]", ""), 
                            Collectors.toList())));

edited Apr 21, 2021 at 20:40

answered Apr 21, 2021 at 20:34

Ryuzaki L

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Eritrean · Accepted Answer · 2021-04-21 20:59:21Z

1

An additional approach which also splits the list of values:

Map<String,List<String>> result = 
     Pattern.compile("[\\r\\n]+")
        .splitAsStream(strBody)
        .map(s -> s.split(":"))
        .map(arr -> new AbstractMap.SimpleEntry<>(
                            arr[0],
                            Arrays.asList(arr[1].replaceAll("[<>]", "").split("\\s*,\\s"))))
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

answered Apr 21, 2021 at 20:59

Eritrean

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Valerij Dobler · Accepted Answer · 2021-04-21 20:36:30Z

0

Your input has two \r\n to separate the entries, you need to split it by it as well, otherwise you will get empty entries, which you then need to filter out.

I'd remove the angle brackets from the string before processing it in the stream. And then only the step of collection remains.

Map<String, String> map = Pattern.compile("\\r?\\n\\r?\\n")
    .splitAsStream(strBody.replaceAll("[<>]",""))
    .map(s -> s.split(":"))
    .collect(Collectors.toMap(e -> e[0], e-> e[1]));

answered Apr 21, 2021 at 20:36

Valerij Dobler

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user4910279 · Accepted Answer · 2021-04-21 21:35:41Z

0

Try this.

String strBody = "key_a:<value_a1>\r\n\r\nkey_b:<value_b1>\r\n\r\nkey_c:<value_c1, value_c2, value_c3>";
Map<String, List<String>> result = Arrays.stream(strBody.split("\\R\\R"))
    .map(e -> e.split(":", 2))
    .collect(Collectors.toMap(a -> a[0],
        a -> List.of(a[1].replaceAll("^<|>$", "").split("\\s,\\s*"))));
System.out.println(result);

output

{key_c=[value_c1, value_c2, value_c3], key_b=[value_b1], key_a=[value_a1]}

answered Apr 21, 2021 at 21:35

user4910279

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