Question

I’m trying to establish some way of mapping a String document to a HashMap as follows:

the String contains key/value pair

$key1=value1
$key2=value2 value21
value22
$key3=value3

what I want to end up with is:

key1, value1
key2, value2 value21\nvalue22
key3, value3

Is there a pattern I can use for this? It looks like an interesting puzzle, so far I have come up with using split("[$]{1}[A-Za-z]+[=]{1}") to separate the different values but then it has to be a different iteration to identify the keys, so I’m looking for a more elegant solution.

Answer 1

You must use two regex here:
\$(\w+)=((\w+\s*)+) will separate keys from values
(\s+) to split values.

String input = "$key1=value1\n" +
        "$key2=value2 value21\n" +
        "value22\n" +
        "$key3=value3";

Pattern keyValuePattern = Pattern.compile("\\$(\\w+)=((\\w+\\s*)+)");
Matcher keyValueMatcher = keyValuePattern.matcher(input); // get a matcher object
Map<String, List<String>> map = new HashMap<String, List<String>>();
while (keyValueMatcher.find()) {
    String key = keyValueMatcher.group(1);
    List<String> values;
    values = Arrays.asList(keyValueMatcher.group(2).split("\\s+"));
    //If you want to update your lists later comment the line above and uncomment those two
    //values = new ArrayList<String>();
    //values.addAll(Arrays.asList(keyValueMatcher.group(2).split("\\s+")));

    map.put(key, values);
}

System.out.println(map); // {key3=[value3], key2=[value2, value21, value22], key1=[value1]}

NB: You could use \$(\w+)=(.*) as regex too, it depends on what you want to match, in the case above, every word/number separated by spaces, in this case, anything.