将字符串转成整数的函数给我看一下吗，简单看一下代码基本功。要求：不要调用parseInt等转换函数

import javax.net.ssl.SSLContext;

/**
 * 字符串转为int
 * @author   IT                      
 * @Date	 2018年10月16日 	 
 */
public class StringToInt {

	public static void main(String[] args) {
		String s = "2018";
		
		try {
			System.out.println("转换结果"+parse(s));
		} catch (Exception e) {
			e.printStackTrace();	
		}
	}
	

	
	public static int parse(String s) throws Exception{
	    int result = 0;
	    if (s == null || s.length() == 0) {
	      throw new Exception("字符串为空");
	    }
	    
		 String s1 = s;
//			if(s.startsWith("-")) {
//				s1 = s.substring(1, s.length());	
//		}
			
    for (int i = 0; i < s1.length(); i++) {
        if (i==0) {
          if(s1.charAt(i) == ‘-‘ ){
            continue;
          }
        }else{
          if(s1.charAt(i)>‘9‘ || s1.charAt(i)<‘0‘){
            throw new Exception("字符串格式错误");
          }
        }
        result = result * 10;
        result = ( result + s1.charAt(i) ) - ‘0‘;
        System.out.println("每一位数："+s1.charAt(i));
        System.out.println("每一次累加结果："+result);
      }
      return result;
	}
}