1

有一个文件Activites.dat，其格式如下：

日
ActivityName
SupervisorName
位置
是否已支付？

例如数据

Sunday
Advanced Open Water Dive Certificate
Mr.Jones
N/A
Yes

Sunday
Sailing
Mr. Jackson
N/A
Yes

Sunday
Generation Next
Ms.Steele
N/A
Yes

现在，我在一个框架上有一个按钮，它显示了表格中当前选定活动的所有信息，并且框架工作正常；所选活动的所有数据都正确显示。

我现在需要做的是，当btnSave按下按钮时，保留原始值进行匹配Activities.dat以找出需要编辑/替换的数据，存储用户当前输入的数据，然后新数据替换中的旧数据Activities.dat

例如想要的结果

最初的

Sunday
Advanced Open Water Dive Certificate
Mr.Jones
N/A
Yes

Sunday
Sailing
Mr. Jackson
N/A
Yes

Sunday
Generation Next
Ms.Steele
N/A
Yes

编辑版本

Sunday
Advanced Open Water Dive Certificate
Mr.Jones
N/A
Yes

**Monday**
**Sailing Elite Course**
**Mr.Jonathan**
**HS5**
**No**

Sunday
Generation Next
Ms.Steele
N/A
Yes

我当前（不工作）的代码

    private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        

//ALL "original-" STRINGS ARE INITIALISED BEFORE

        String nActivityName  =   txtActivityName.getText();
        Object nDay  =   comboboxDay.getSelectedItem().toString();
        String nSupervisor = txtSupervisor.getText();
        String nLocation = txtLocation.getText();
        String nPaid = null;

        //Check which option is selected: Paid or Not Paid
        if(radioYes.isSelected())
        {
            nPaid = radioYes.getText();
        }
        if(radioNo.isSelected())
        {
            nPaid = radioNo.getText();
        }

        File file = new File("Activities.dat");

        try{
                BufferedReader reader = new BufferedReader(new FileReader(file));
                BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));

                while(reader.ready())
                {
                    String RDay = reader.readLine();    
                    String RActivityName = reader.readLine();
                    String RSupervisor = reader.readLine();
                    String RLocation = reader.readLine();
                    String RPaid = reader.readLine();
                    String nothing = reader.readLine();

                    //Match the exact same set of data as the original activity's data before edit.
                    if(RActivityName.equals(originalActivityName))
                    {
                        RDay.replace(RDay, (CharSequence) nDay);
//                                = nDay.toString();
                        RActivityName = nActivityName;
                        RSupervisor = nSupervisor;
                        RLocation = nLocation;
                        RPaid = nPaid;
                        nothing = nothing;
                    }
                    System.out.println(RDay + RActivityName + RSupervisor + RLocation + RPaid);
                }


        }
        catch(IOException e)
        {
                Logger.getLogger(AddActivity.class.getName()).log(Level.SEVERE, null, e);
        }

    }

我可以存储原始值以进行比较并获取新数据，但我不知道如何用Activities.dat. 我该怎么做呢？

是的，我知道我有一个BufferedReader，但我没有使用它，因为我不知道在这种特殊情况下在哪里或如何使用它。

4

1 回答 1

1

这是执行“读/写整个文件”方法的一种方法：

  1. 创建一个封装单个活动的类，因此您可以在比一堆字符串更高的级别上实现逻辑：

    class Activity {
  String day;
  String activityName;
  String supervisorName;
  String location;
  String paid;
}

    这是一个非常粗略的课程大纲。为简洁起见，我没有包含适当的构造函数、getter hashCode()、equals()和toString().

  2. 创建另一个只关心从/向文件读取和写入活动的类。这再次使您的代码更易于理解。

    想想你想从那个类中得到什么，这些应该是调用者唯一可见的方法，例如

    /** Write activities to a file. */
void writeActivities(File file, List<Activity> activities);

/** Read activities from a file. */
List<Activity> readActivities(File file);

    然后实现方法，例如

    public class ActivityManager {
  // Don't rely on te platform default, use a fixed charset.
  private final static Charset UTF_8 = Charset.forName("UTF-8");

  /** Write activities to a file. */
  void writeActivities(File file, List<Activity> activities)
      throws IOException {
    try (PrintWriter out = new PrintWriter(
        new OutputStreamWriter(new FileOutputStream(file), UTF_8))) {
      boolean first = true;
      for (Activity activity : activities) {
        if (!first) {
          // Print a newline after every activity.
          out.println();
        }
        writeActivity(out, activity);
        if (first) {
          first = false;
        }
      }
    }
  }

  private void writeActivity(PrintWriter out, Activity activity) {
    out.println(activity.day);
    out.println(activity.activityName);
    out.println(activity.supervisorName);
    out.println(activity.location);
    out.println(activity.paid);
  }

  /** Read activities from a file. */
  List<Activity> readActivities(File file) throws IOException {
    try (BufferedReader in = new BufferedReader(
           new InputStreamReader(new FileInputStream(file),
        UTF_8))) {
      List<Activity> result = new ArrayList<Activity>();
      while (true) {
        Activity activity = readActivity(in);
        result.add(activity);

        String line = in.readLine();
        if (line == null) {
          break; // Reached end of file.
        }
        if (!line.equals("")) {
          throw new IllegalStateException(
            "Expected empty line but got: <" + line + ">");
        }
      }
      return result;
    }
  }

  private Activity readActivity(BufferedReader in) throws IOException {
    Activity activity = new Activity();
    activity.day = in.readLine();
    activity.activityName = in.readLine();
    activity.supervisorName = in.readLine();
    activity.location = in.readLine();
    activity.paid = in.readLine();
    return activity;
  }
}

    上面的代码依赖于 Java 7 中引入的try-with-resources 功能。对于早期版本的 Java，您需要try通过恢复为链接中显示的通常的 declare-try-finally-close 样式来重写这两个块。

  3. 从您的 UI 事件处理代码（如actionPerformed()方法）中，只需调用一个实例ActivityManager来读取和写入活动并在您的 UI 组件和Activity类之间进行转换。

于 2013-03-17T11:04:09.603 回答