public class StrToInt {
public static final String Min_number = "-9223372036854775808";
public static final String Max_number = "9223372036854775807";

public static Long strToNumber(String s) {
    long number = 0;
    // 需要先判断是否为空，再判断是否为空串 否则会报空指针异常
    if (s == null || s.equals("")) {
        System.out.println("传入的字符串为空或空指针！");
        return (long) 0;
    }
    boolean isNum = s.matches("-{0,1}[0-9]+");
    if (!isNum) {
        System.out.println("输入的数字不合法！");
        return (long) 0;
    }
    if (s.startsWith("-")) {
        if (s.length() > Min_number.length()) {
            System.out.println("该字符串超过数字的下届");
            return (long) 0;
        }
        if (s.length() == Min_number.length() && s.compareTo(Min_number) > 0) {
            System.out.println("该字符串超过数字的下届");
            return (long) 0;
        }
    } else {
        if (s.length() > Max_number.length()) {
            System.out.println("该字符串超过数字的上届");
            return (long) 0;
        }
        if (s.length() == Max_number.length() && s.compareTo(Max_number) > 0) {
            System.out.println("该字符串超过数字的上届");
            return (long) 0;
        }
    }

    number = Long.parseLong(s);
    return number;
}

public static void main(String[] args) {
    System.out.println(strToNumber("-666"));
    System.out.println(strToNumber("666"));
    System.out.println(strToNumber(""));
    System.out.println(strToNumber(null));
    System.out.println(strToNumber("1a9"));
    System.out.println(strToNumber("-9223372036854775809"));
    System.out.println(strToNumber("9223372036854775808"));
}

}