递归求 1 + 2 + 3 + ... + 10

public class Test{
    public static void main(String[] args) {
        int num = 10;
        System.out.println(sum(num));
    }

    public static int sum(int a) {
        if (a == 1){
            return 1;
        }else{
            return a + sum (a - 1);
        }
    }
}