Google Interview - Compress String to i18n

i18n (where 18 stands for the number of letters between the first i and the last n in the word “internationalization,”) Wiki it. 

Generate all such possible i18n strings for any given string. for eg. "careercup"=>"c7p","ca6p","c6up","car5p","ca5up","care4p","car4up","caree3p","care3up"..till the count is 0 which means its the complete string again.

public List<String> compress(String s) {
	List<String> list = new ArrayList<>();
	if(s == null) return list;
	int n = s.length();
	if(n <= 2) {
		list.add(s);
		return list;
	}
	for(int i=1; i<=n-2; i++) {
		for(int j=1; i+j<n; j++) {
			list.add(s.substring(0,j)+i+s.substring(i+j));
		}
	}
	return list;
}

Reference:

http://latest.careercup.appspot.com/question?id=5733696185303040