JAVA IO 标准输入输出流

摘自 b站尚硅谷JAVA视频教程

BufferedReader br = null;
        try {
            InputStreamReader isr = new InputStreamReader(System.in);
            br = new BufferedReader(isr);
            while (true){
                String s = br.readLine();
                if("exit".equals(s)){
                    break;
                }
                System.out.println(s.toUpperCase());
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if(br!=null)
                    br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }