PrintWriter附加方法不附加 | PrintWriter附加方法不附加

本文介绍了PrintWriter附加方法不附加的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

以下方法仅写出我添加的最新项目，它不会附加到以前的条目。我做错了什么？

The following method only writes out the latest item I have added, it does not append to previous entries. What am I doing wrong?

public void addNew() {
    try {
        PrintWriter pw = new PrintWriter(new File("persons.txt"));
        int id = Integer.parseInt(jTextField.getText());
        String name = jTextField1.getText();
        String surname = jTextField2.getText();
        Person p = new Person(id,name,surname);
        pw.append(p.toString());
        pw.append("sdf");
        pw.close();
    } catch (FileNotFoundException e) {...}
}

推荐答案

PrintWriter 的方法被称为 append（）的事实不会意味着它改变了正在打开的文件的模式。

The fact that PrintWriter's method is called append() doesn't mean that it changes mode of the file being opened.

您还需要在追加模式下打开文件：

You need to open file in append mode as well:

PrintWriter pw = new PrintWriter(new FileOutputStream(
    new File("persons.txt"),
    true /* append = true */));

另请注意，文件将以系统默认编码写入。它并不总是需要并且可能导致互操作性问题，您可能希望明确指定文件编码。

Also note that file will be written in system default encoding. It's not always desired and may cause interoperability problems, you may want to specify file encoding explicitly.

这篇关于PrintWriter附加方法不附加的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！