Calculate student grade and write to disk Java

Topic: There are five students, each student has scores of 3 courses, input the above data from the keyboard (including student ID, name, scores of the three courses), calculate the average score, and combine the original data and the calculated average The score is stored in the disk file "stud".

import java.io.*; 
import java.util.*; 
public class writeGrade {
    
     
	public static void main(String[] args){
    
    
		Scanner ss = new Scanner(System.in);
		String [][] a = new String[5][6];
		for(int i=1; i<6; i++) {
    
    
	    	System.out.print("请输入第"+i+"个学生的学号：");
	    	a[i-1][0] = ss.nextLine();
	   		System.out.print("请输入第"+i+"个学生的姓名：");
	    	a[i-1][1] = ss.nextLine();
		    for(int j=1; j<4; j++) {
    
    
		    	System.out.print("请输入该学生的第"+j+"个成绩：");
		    	a[i-1][j+1] = ss.nextLine();
		    }
		    System.out.println("\n");
		}
		//以下计算平均分
	   float avg;
	   int sum;
	   for(int i=0; i<5; i++) {
    
    
			sum=0;
		    for(int j=2; j<5; j++) {
    
    
		    	sum=sum+ Integer.parseInt(a[i][j]);
		    }
		    avg= (float)sum/3;
		    a[i][5]=String.valueOf(avg);
	    }
	    //以下写磁盘文件
	    String s1;
	    try {
    
    
		    File f = new File("C:\\stud");
		    if(f.exists()){
    
    
		    System.out.println("文件存在");
		    }else{
    
    
		    System.out.println("文件不存在，正在创建文件");
		    f.createNewFile();//不存在则创建
		    }
		    BufferedWriter output = new BufferedWriter(new FileWriter(f));
		    for(int i=0; i<5; i++) {
    
    
		    	for(int j=0; j<6; j++) {
    
    
			    	s1=a[i][j]+"\r\n";
			    	output.write(s1);
		    	}
		    }
	    	output.close();
	    	System.out.println("数据已写入c 盘文件stud 中!");
	    } catch (Exception e) {
    
    
	    	e.printStackTrace();
	    }
	}
}