System.out.println("input a number");

int n=Integer.parseInt(br.readLine(System.in));

解决方法@H_404_15@

需要在BufferedReader的构造函数中指定InputStreamReader. InputStreamReader将字节流转换为字符流.正如其他人所提到的那样,可以认识到可以从这段代码抛出的异常,例如IOException和NumberFormatException.

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("input a number");
int n = Integer.parseInt(br.readLine());