You are playing the following Flip Game with your friend: Given a string that contains only these two characters: + and -, you and your friend take turns to flip two consecutive "++" into "--". The game ends when a person can no longer make a move and therefore the other person will be the winner.

Write a function to compute all possible states of the string after one valid move.

For example, given s = "++++", after one move, it may become one of the following states:

[
  "--++",
  "+--+",
  "++--"
]

If there is no valid move, return an empty list [].

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List result = new ArrayList();
        for(int i=1;i<s.length();i++){
            if(s.charAt(i) == '+' && s.charAt(i-1) == '+'){
                String news = new String(s.substring(0,i-1)+"--"+s.substring(i+1,s.length()));
                result.add(news);
            }
        }
        return result;
    }
}