剑指offer表示数值的字符串

public boolean isNumber(String s) {
    if(s == null || s.length() == 0){
        return false;
    }
    boolean numSeen = false;
    boolean dotSeen = false;
    boolean eSeen = false;
    char[] str = s.trim().toCharArray();
    for(int i = 0;i < str.length; i++){
        if(str[i] >= '0' && str[i] <= '9'){
            numSeen = true;
        }else if(str[i] == '.'){
            if(dotSeen || eSeen){
                return false;
            }
            dotSeen = true;
        }else if(str[i] == 'e' || str[i] == 'E'){
            if(eSeen || !numSeen){
                return false;
            }
            eSeen = true;
            numSeen = false;
        }else if(str[i] == '-' || str[i] == '+'){
            if(i != 0 && str[i-1] != 'e' && str[i-1] != 'E'){
                return false;
            }
        }else{
            return false;
        }
    }
    return numSeen;
}