填空题

[说明] 编写一个Application，从键盘输入整数n，并计算从1到n的累加和。
import java. io. *;
public class Application1
public static void main(String [] args)
String s = " ";
int n, sum = 0;
System. out. println (“计算从1到n 的累加和。”);
System. out. print( “请输入n的值:”);
try
(1)
BufferedReader br = new BufferedReader(isr);
(2)

catch(Exception e)
(3)
for(int i=l; i＜ =n; i++)
(4)
System. out. println ( “你刚才的输入是：” + n);
System. out. println ( “1到n的累加和是：”+ sum);