split string and store it into HashMap java 8

Unless Splitter is doing any magic, the getTokenizeString method is obsolete here. You can perform the entire processing as a single operation:

Map<String,String> map = Pattern.compile("\\s*-\\s*")
    .splitAsStream(responseString.trim())
    .map(s -> s.split("~", 2))
    .collect(Collectors.toMap(a -> a[0], a -> a.length>1? a[1]: ""));

By using the regular expression \s*-\s* as separator, you are considering white-space as part of the separator, hence implicitly trimming the entries. There’s only one initial trim operation before processing the entries, to ensure that there is no white-space before the first or after the last entry.

Then, simply split the entries in a map step before collecting into a Map.

First of all, you don't have to split the same String twice.
Second of all, check the length of the array to determine if a value is present for a given key.

HashMap<String, String> map= 
    list.stream()
        .map(s -> s.split("~"))
        .collect(Collectors.toMap(a -> a[0], a -> a.length > 1 ? a[1] : ""));

This is assuming you want to put the key with a null value if a key has no corresponding value.

Or you can skip the list variable :

HashMap<String, String> map1 = 
    MyClass.getTokenizeString(responseString, "-")
        .stream()
        .map(s -> s.split("~"))
        .collect(Collectors.toMap(a -> a[0], a -> a.length > 1 ? a[1] : ""));