public class String2Int {    public static void main(String[] args) {        int i = parseInt("-12306");        System.out.println(i);    }     public static int parseInt(String s) {        if (s == null || s.equals(""))            throw new IllegalArgumentException("参数不能为null或空串！");         int result = 0;        boolean isFu = false;        for (int i = 0, len = s.length(); i < len; i++) {            char c = s.charAt(i);            if(i==0 && c == '-'){            	isFu = true;            	continue;            }            if (c >= '0' && c <= '9') {                result = result * 10 + (c - '0');            } else {                throw new IllegalArgumentException("s中只能包含数字");            }        }         return isFu ? -result : result;    }}