把一个字符串转化成整数

/** * @author David * 将字符串转换成数字，重点考察正负号，输入的不是数字字符的情况 */public class Example3 {public static void main(String[] args) {// TODO Auto-generated method stubScanner scanner = new Scanner(System.in);String s = scanner.next();Example3 example3 = new Example3();example3.fun(s);}private void fun(String s) {if (s != null) {String str;if (s.charAt(0) == '-') {str = s.substring(1, s.length());fun2(str, false);} else {str = s;fun2(str, true);}}}private void fun2(String s, boolean isPos) {int value = 0;for (char c : s.toCharArray()) {if (c > '9' || c < '0') {System.out.println("error input!");return;}}for (int i = 0; i < s.length(); i++) {value = 10 * value + s.charAt(i) - '0';}if (!isPos) {value = -value;} System.out.println(value);}}