Question

到目前为止我所理解的是，它将逐行读取文件，同时，它将拆分记录并将其保存在字段数组中，之后我无法理解它将添加的内容记录列表....因为它直接将fields数组添加到列表中。

String fileName = "C:\\data.csv"

public static Collection<String[]> getTestData(fileName) throws IOException {
    List<String[]> records = new ArrayList<String[]>();
    String record;
    BufferedReader file = new BufferedReader(new FileReader(fileName));
    while ((record=file.readLine())!=null) {
        String fields[] = record.split(",");
        records.add(fields);
    }
    file.close();
    return records;
}

CSV文件

160,45,17.6,Underweight
168,70,24.8,Normal
181,89,27.2,Overweight
178,100,31.6,Obesity

Answer 1

设置字符串数组列表。
从data.csv
对于每一行，使用逗号作为分隔符拆分为数组，并将数组添加到列表中
返回列表。

编辑：

你最终得到的是一个字符串数组列表。

如果您的csv文件如下所示：

ABC，123

RTF，434

LMO，554

然后你的字符串arrys列表如下所示：

list item 1：String [] {“abc”，“123”}

list item 2：String [] {“rtf”，“434”}

list item 3：String [] {“lmo”，“554”}

Answer 2

使用以下内容声明

records：

List<String[]> records ...

这意味着它是一个字符串数组列表。

列表中的每个项目都将具有String[]

类型

fields是一个数组，所以当执行folloiwng行时

records.add(fields);

它将fields数组添加到列表中。

Answer 3

String fileName = "C:\\data.csv" //set the location of a comma seperated value file

public static Collection<String[]> getTestData(fileName) throws IOException {
    List<String[]> records = new ArrayList<String[]>(); // instantiate an array list object to hold the fields to be returned
    String record;
    BufferedReader file = new BufferedReader(new FileReader(fileName)); // open the file for reading
    while ((record=file.readLine())!=null) { //read the file line by line, execute the code in the curly brackets until an empty line or end of file is reached
        String fields[] = record.split(","); //split up each line into an array, each elemet will be delimited by a comma
        records.add(fields); // add each element to the array list object created earlier
    }
    file.close();
    return records; //return all the fields found in the file
}

例如，文件包含：

one,two,three
red,green,gold

此方法将返回一个字符串数组列表：

{ "one","two","three" }
{ "red","green","gold" }

修改：

对于您添加的数据，这将返回一个数组列表：

{ 160, 45, 17.6, Underweight }
{ 168, 70, 24.8, Normal }
{ 181, 89, 27.2, Overweight }
{ 178, 100, 31.6, Obesity }

Answer 4

该方法使用List。

这很像一个数组数组，除了外部数组是动态的。

String＃split返回一个字符串数组。我们将该数组添加到列表中，并在最后返回数组列表。

Answer 5

String fileName = "C:\\data.csv"       // This is the file to be read

// Method is public: can be called from anywhere in the package and class
//           static so can be called without instance.
//           return type is Collection<String []> Collection Of String Array
//           takes filename as argument
//           throws IOException since we are reading from a file

public static Collection<String[]> getTestData(fileName) throws IOException {

    // record is the List which is a Collection of String Arrays we will return
    List<String[]> records = new ArrayList<String[]>();

    String record;

    // Reading the File
    BufferedReader file = new BufferedReader(new FileReader(fileName));

    // Read line by line unless the last line is null
    while ((record=file.readLine())!=null) {
        String fields[] = record.split(",");   // splits the line with delimiter ","
        records.add(fields);
    }
    file.close();   // Close the file
    return records; // return the Collection
}

split()

需要了解这个java代码的工作原理

5 个答案: