为什么输出的学号不是1-20；而是01.11.21....191（i+1）

public class ExerTest2 {
    public static void main(String[] args) {
        Student[] s1 = new Student[20];
        for(int i = 0;i < s1.length;i++) {
            s1[i] = new Student();
            
            s1[i].state = (int)(Math.random()*(6-1+1)+1);
            s1[i].score = (int)(Math.random()*(100-0+1));
        }
          for(int i = 0;i < s1.length;i++) {
             
                  System.out.println("学号:" +  i+1 + " 年级:"  +  s1[i].state + " 成绩:" + s1[i].score);
              
          }
    } 
}
class Student{
    int number;
    int state;
    int score;
}

i+1加个括号就好啦