public class WriteReadFiles {    private static Logger log = LoggerFactory.getLogger(WriteReadFiles.class);    public boolean writeFile(String content) {        String filename = "E:/java_src/MVCDemo3/MVCDemo3/accounts.txt";        try {            File f = new File(filename);            if (!f.exists()) {                f.createNewFile();            }            OutputStreamWriter write = new OutputStreamWriter(new FileOutputStream(f));            BufferedWriter writer = new BufferedWriter(write);            writer.write(content);            writer.flush();             write.close();            writer.close();            log.debug("Write File complete!");            return true;        }catch (Exception e){            e.printStackTrace();        }        return false;    }

使用BufferedWriter 将内容写入文件，先开始少了wriite.flush()这句，发现无法写入内容。查资料后发现，原来BufferedWriter是缓冲输入流，意思是当你调用BufferedWriter的write方法时候。数据是先写入到缓冲区里，并没有直接写入到目的文件里。你必须调用BufferedWriter的flush()方法。这个方法会刷新一下该缓冲流，也就是会把数据写入到目的文件里。必须有这句的样子，实践中如果没有writer.flush(); 仅有writer.close();，会报异常。