package myPackage;
public class Main {
static int n=1,count=0;
static String s;
static char[]ch;
public static void main(String[]args) {
while(n<=2020) {
s=String.valueOf(n);
ch=s.toCharArray();
for(char c:ch) {
if(c=='2') {
count++;
}
}
n++;
}
System.out.println(count);
}
}
结果为:624