Split a text without whitespaces by words in list

Coiiin :

I have three lists, that I have merged into one list

    static List allLists = Stream.of(list1, list2, list3)
        .flatMap(Collection::stream)
        .collect(Collectors.toList());

I have user input without whitespaces

String = "HelloIwanttobookanonlineseminaratyourcompany"

All the words in the user input String are already in allLists. I want to iterare over allLists and insert whitespaces into the String, with every word found. The result should be:

String = "Hello I want to book an online seminar at your company"

Is there an easy solution I miss?

Bohemian :

Use a one-liner that employs a (massive) look behind built from allLists to insert spaces before each word:

str = str.replaceAll("(?<=" + String.join("|", allLists) + ")", " ");

Note that order of words in allLists is important; if you want longer words to take preference, list them first (recommended). Eg if both "book" and "booking" are in your list, put booking before book, otherwise you’ll get "book ing" in your result.