描述

10.2 Rolling Project Part 8
10.2 滚动项目第 8 部分

We will be introducing static fields, file reading and writing, and exception handling.
我们将介绍静态字段、文件读写和异常处理。

You have been given the following updated class diagram.
您已获得以下更新的类图。

PART - A 部件 - A

Refer to the legend in the diagram to help infer what changes will be made to the code from Part 9.
请参阅图中的图例，以帮助推断 Part 9 中的代码将进行哪些更改。

Using the workspaces, access the rolling project workspace and do the following:
使用工作区，访问滚动项目工作区并执行以下操作：

We need to create the FileIO class.
我们需要创建 FileIO 类。
- Create the template for the FileIO class.
  为 FileIO 类创建模板。
- Since we are using FileIO as a class, we will need to write your program such that the actual parsing of the file contents has to be done in another class and not the FileIO class as this would violate the responsibility-driven design concept for the class.
  由于我们将 FileIO 用作一个类，因此我们需要编写您的程序，以便文件内容的实际解析必须在另一个类中完成，而不是在 FileIO 类中完成，因为这将违反该类的责任驱动设计概念。
- When reading the file remember to read each line and then add a delimeter. This can be anything except , or -. This will make it easier for us to identify each line in the file when we parse the contents in another class. Now write the readFile() method.
  读取文件时，请记住读取每一行，然后添加分隔符。这可以是除、或 - 之外的任何值。这将使我们在解析另一个类中的内容时更容易识别文件中的每一行。现在编写 readFile（） 方法。
- The write file method simply accepts a string and writes it to the file. Similar to the readFile() method above, when we create the string, we need to make sure to identify each new line in our file (but we will do this in another method). For now, write the writeFile() method.
  write file 方法只接受一个字符串并将其写入文件。与上面的 readFile（）方法类似，当我们创建字符串时，我们需要确保识别文件中的每个新行（但我们将在另一个方法中执行此操作）。现在，编写 writeFile（） 方法。

PART - B 部件 - B

Refer to the legend in the diagram to help infer what changes will be made to the code from Part 10A.
请参阅图中的图例，以帮助推断将对 Part 10A 中的代码进行哪些更改。

Using the workspaces, access the rolling project workspace and do the following:
使用工作区，访问滚动项目工作区并执行以下操作：

If your Part 8 is complete, you will need to modify the University, FileIO, Unit and Student Class.
如果您的第 8 部分已完成，您将需要修改 University、FileIO、Unit 和 Student Class。
We will be introducing static fields, file reading and writing, and exception handling.
我们将介绍静态字段、文件读写和异常处理。
First, if a text file called 'students.txt' is not present within your Rolling Project workspace, then create a text file with the following data in it.
首先，如果您的 Rolling Project 工作区中没有名为 'students.txt' 的文本文件，则创建一个包含以下数据的文本文件。

3 Sep 2018,Lucy,Caulfield,12345678,lucy@monash.edu,FIT9131-Java Programming-6;FIT9132-Databases-6 1 Jan 2018,Stacey,Carnegie,87654321,stacey@monash.edu,FIT9131-Java Programming-6;FIT9132-Databases-6 28 Apr 2018,Jacquie,Ormond,06660666,jacquie@monash.edu,FIT9131-Java Programming-6;FIT9132-Databases-6 12 Dec 2018,Sarah,Melbourne,12121212,sarah@monash.edu,FIT9131-Java Programming-6;FIT9132-Databases-6
2018 年 9 月 3 日，Lucy，Caulfield，12345678，lucy@monash.edu，FIT9131-Java 程序设计-6;FIT9132 数据库 6 2018 年 1 月 1 日，Stacey，卡内基，87654321，stacey@monash.edu，FIT9131-Java 程序设计-6;FIT9132 数据库 6 2018 年 4 月 28 日，Jacquie，Ormond，06660666，jacquie@monash.edu，FIT9131-Java 程序设计-6;FIT9132 数据库 6 2018 年 12 月 12 日，Sarah，墨尔本，12121212，sarah@monash.edu，FIT9131-Java 程序设计-6;FIT9132 数据库 6

Next, we modify the code in our University class.
接下来，我们修改 University 类中的代码。
- First, let's introduce some constants into our program. Declare two constants as fields in your class. One should store the input text filename and the other should store the output text filename. This way should the filenames change we only need to modify the code in one place.
  首先，让我们在程序中引入一些常量。将两个常量声明为类中的字段。一个应存储输入文本文件名，另一个应存储输出文本文件名。这样，如果文件名发生变化，我们只需要在一个地方修改代码。
- Next we modify the inputUnitDetails() and inputUnitDetailsOnce() methods. Since these methods are accepting an integer input for the credit points, entering anything non-numeric will crash our program. So modify it to use exception handling and preferably a loop that allows the user to re-enter until a correct value is entered. See the hints section below if you cannot figure this out.
  接下来，我们修改 inputUnitDetails（） 和 inputUnitDetailsOnce（） 方法。由于这些方法接受信用点的整数输入，因此输入任何非数字都会使我们的程序崩溃。因此，请对其进行修改以使用异常处理，最好使用允许用户重新输入直到输入正确值的循环。如果您无法弄清楚这一点，请参阅下面的提示部分。
- Next, we write the readFile() method. This method should read the contents using the FileIO class and then store it into the ArrayList<Enrolment> in the university. See the hints section below if you are unable to determine how the reading should be done.
  接下来，我们编写 readFile（） 方法。此方法应使用 FileIO 类读取内容，然后将其存储到大学的 ArrayList 中。如果您无法确定应该如何进行读取，请参阅下面的提示部分。
- Next, we write the writeFile() method. This method should pass the collection - ArrayList<Enrolment> as a single object to the FileIO class to be written to the file. See the hints section below if you are unable to determine how the writing should be done for multiple lines.
  接下来，我们编写 writeFile（） 方法。此方法应将集合 - ArrayList 作为单个对象传递给要写入文件的 FileIO 类。如果您无法确定应该如何为多行进行编写，请参阅下面的提示部分。
Next, we modify the code in our University, Enrolment, Student and Unit classes:
接下来，我们修改 University、Enrolment、Student 和 Unit 类中的代码：
- Next, we need to update the display method in the Enrolment, Student and Unit class so that method will print the state of the object using System.out.println and add the toString method to return the String(holding the state of the object) in University, Enrolment, Student and Unit class.
  接下来，我们需要更新 Enrolment， Student 和 Unit 类中的 display 方法，以便该方法使用 System.out.println 打印对象的状态，并添加 toString 方法以返回 University， Enrolment， Student 和 Unit 类中的 String（保存对象的状态）。
Finally, we modify the code in our University class again:
最后，我们再次修改 University 类中的代码：
- Lastly, modify the startProgram() method, so when the program starts, it first reads the file and stores the details in the collection. And when the program ends, it writes the content of the collection to the file.
  最后，修改 startProgram（） 方法，以便在程序启动时，它首先读取文件并将详细信息存储在集合中。当程序结束时，它会将集合的内容写入文件。
- Now run your program. 现在运行您的程序。

Hints 提示

When working with files, the \r\n delimeters should be used to indicate a new line within a text file. If a string contains these characters it will automatically show the text on a new line. This method works for most systems.
处理文件时，应使用 \r\n 分隔符来指示文本文件中的新行。如果字符串包含这些字符，它将自动在新行上显示文本。此方法适用于大多数系统。
When accepting numeric input it is always a good idea to read the input as a String. If using the Scanner class, the nextLine() method should be used. To ensure that the input is actually a string, within a try..catch block, the String can be converted to an int using the method Integer.parseInt(). Look up the API to understand how this method works.
当接受数字输入时，最好将输入读取为 String。如果使用 Scanner 类，则应使用 nextLine（） 方法。为了确保输入实际上是一个字符串，在 try..catch 块，可以使用 Integer.parseInt（） 方法将 String 转换为 int。查找 API 以了解此方法的工作原理。
To separate the contents being read from your file, use the split() method in the String class. Read the API to better understand how this method works. Remember, if when reading you introduce a new delimeter, you will have to split twice. The first to get the original file contents line by line, the second so you can split each original line into its individual data.
Remember to use exception handling correctly to ensure that your program does not crash no matter what the user does.
Remember to write your code one step at a time as outlined above to ensure no mistakes creep in.

描述

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