regular expression for finding string between [[ ]] and {{}}

regular expression for finding string between [[ ]] and {{}}

How could I find string between [[]]? After searching a answer I find this
method below, but I cannot find the regular expression for [[]], neither
for {{}}.
What I want to do is to find e.g. [[abc]]XXXXXXXXXX[[def]], and save abc,
def as a arraylist.
String s = "[[abc]]XXXXXXXXXX[[def]]";
Pattern p = Pattern.compile("[[(.*?)]]")
Matcher m = p.matcher(s);
if (m.find()) {
System.out.println(m.group(i)); // => "abc","def"
}
Thanks alot!