public static void main(String[] args) {
        try {
            String line = null;
            StringBuilder builder = new StringBuilder();
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            while ((line = br.readLine()) != null) {
                if (line.equalsIgnoreCase("EOF")){
                    break;
                } else{
                    builder.append(line);
                }
            }
            String ss = builder.toString();
            System.out.println(ss.replaceAll("you", "we"));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

------解决方案--------------------
使用别的结束符，只要可以标识结束就可以。