英文:
how do i use a scanner to read a file object
问题
从File类中获取的文件对象，然后使用包装在其中的Scanner对象来读取文件，假设文件中包含如下示例：
Student{name=Jill Gall,age=21,gpa=2.98}
要将其分隔成字段，然后跳过下一步，因为我只需在此处调用setter方法，然后设置这些值。接下来，我想将这些字段保存为一个Student对象，然后将这些对象保存在一个数组中以便返回。
我并不是真的在寻找整个问题的解决方案，我只是想知道如何调用包装在File对象周围的Scanner对象以对其进行读取。我可以使用子字符串来获取字段并将它们保存到新字段中，我相当确定我可以使用for循环将它们加载到一个可以返回的数组中。我之所以将整个问题都列出来，是为了向您提供关于任务的尽可能详细的信息。
目前，我最好的尝试是这样的：
Scanner n = new Scanner(System.in);
n.commandgoeshere?(filename);
我应该如何让Scanner输出数据，以便我可以获取子字符串并执行上述所需的操作呢？
英文:
like the question how would I use a file object taken from the File class
<https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/io/File.html>
and use a scanner object wrapped around this to read the file,
then say a example like this is contained in the file,
Student{name=Jill Gall,age=21,gpa=2.98}
separate it into fields, skip next step as I just have to call the setters here, and then set the values
I then to save the fields as a Student Object and then save those in a array that I can return?
I'm not really looking for a solution to the entire problem here I'm just wondering as to what the syntax is for calling a scanner object wrapped around a File object to read it, I can use substring to grab the fields to separate and save them onto the new fields, and I'm pretty sure I can just use a for loop to load these onto a array that i can return, the only reason I listed out the entire problem for you guys is so I can give you guys the most details about the task as I can give here
right now my best attempt is this
Scanner n = new Scanner(System.in);
n.commandgoeshere?(filename);
how would I get the scanner to output the data so that i can take a substring and do the stuff i need to do above?
答案1
得分: 0
你必须在扫描器的构造函数中提供一个输入流，目前你正在将系统输入流（来自控制台）提供给扫描器。我认为你正在寻找类似这样的解决方法：
File file = new File("");
try {
Scanner scanner = new Scanner(file);
while (scanner.hasNext()) {
String nextLine = scanner.nextLine();
// 或者使用正则表达式？
String extractedPattern = scanner.next("some pattern");
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
英文:
You have to provide an input stream in the constructor of the scanner, atm you are providing the system input stream (from the console) to the scanner. I think something like this is what you are looking for:
File file = new File("");
try {
Scanner scanner = new Scanner(file);
while (scanner.hasNext()) {
String nextLine = scanner.nextLine();
// or use regex ?
String extractedPattern = scanner.next("some pattern");
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
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