Java中字符串转int数据类型的三种方式

String a = "100";
String b= "50";
int A = Integer.valueOf(a);
int B = Integer.valueOf(b);
 
int c = A+B;
System.out.println(c);

String a = "100";
String b= "50";
int A = Integer.parseInt(a);
int B = Integer.parseInt(b);
 
int c = A+B;
System.out.println(c);

public class String2IntDemo {
    public static void main(String[] args) {
        String a = "100";
        String b = "50";
        int A = string2int(a);
        int B = string2int(b);
        int c = A + B;
        System.out.println(c);
    }
 
    public static int string2int(String s) {
        int num = 0;
        int pos = 1;
        for (int i = s.length() - 1; i >= 0; i--) {
            num += (s.charAt(i) - '0') * pos;
            pos *= 10;
 
        }
        return num;
 
    }
}

String s = "520";
System.out.println(s.charAt(2) - '0');
System.out.println(s.charAt(1) - '0');
System.out.println(s.charAt(0) - '0');