解析Java CSV文件操作

Question

我有以下示例CSV文件

rc,u,s,ui,gh
m,1,8,0,12
n,3,0,0,7
d,1,1,8,0

我想读取此CSV文件并按其名称获取列（例如，s）。用一些值减去提取的列，并在CSV文件中更新该列

有没有一种简单的方法可以用Java实现

Answer 1

String line;
BufferedReader br = new BufferedReader(new FileReader("path_to_your_file"));

while ((line = br.readLine()) != null) { 
       StringTokenizer tokenizer = new StringTokenizer(line, ",");

       while(tokenizer.hasMoreTokens()) {
              String token = tokenizer.nextToken(); 
       } 
}

这样你就可以得到逗号分隔的标记。对它们执行所需操作，然后查看BufferedWriter类以存储回值

Answer 2

你可以用JEzCSV读或写CSV文件，你可以读代码，是开源的

Answer 3

在PHP中，您可以尝试以下方法：

<?php
function csv2PhpArray($sFile,$sSeparator = ';'){
$arrCsv;
$arrCsvKeys;
$i = 0;
    if (($handle = fopen($sFile, "r")) !== false) {
        while (($arrRow = fgetcsv($handle, 1000, $sSeparator)) !== false) {
            //Each row
            $nLenRow = count($arrRow);
            for ($j=0; $j < $nLenRow; $j++) {
                if($i==0){
                    $arrCsvKeys[] = $arrRow[$j];
                }else{
                    $arrCsv[$arrCsvKeys[$j]][] = $arrRow[$j];
                }
            }
            if($i==0) $i++;
        }
        fclose($handle);
    }
    return $arrCsv;
}
function updateCsv($arrCsv,$sFile,$sSeparator = ';'){
    $arrCsvKeys = array_keys($arrCsv);
    $i = 0;
    $nMaxKeys = count($arrCsvKeys);
    $nMax  = count($arrCsv[$arrCsvKeys['0']]);
    $arrInput;
    for($k=0;$k<$nMaxKeys;$k++){
        $arrInput[$i][$k] = $arrCsvKeys[$k];
    }
    for($j=0;$j<$nMax;$j++){
        $i++;
        for($k=0;$k<$nMaxKeys;$k++){
            $arrInput[$i][$k] = $arrCsv[$arrCsvKeys[$k]][$j];
        }
    }

    $nMax  = count($arrInput);
    $fp = fopen($sFile, 'w');
    for($i=0;$i<$nMax;$i++){
        fputcsv($fp, $arrInput[$i]);
    }

    fclose($fp);
}

$arrCsv = csv2PhpArray('file.csv',';');
echo '<pre>';
var_dump($arrCsv);
echo '</pre>';
$nMax = count($arrCsv['s']);
for($i=0;$i<$nMax;$i++){
    $arrCsv['s'][$i]= intval($arrCsv['s'][$i])+10;
}
echo '<pre>';
var_dump($arrCsv);
echo '</pre>';
updateCsv($arrCsv,'file2.csv',';');
echo '<pre>';
var_dump(csv2PhpArray('file2.csv',';'));
echo '</pre>';
?>

我放了两个文件（file.csv和file2.csv）来查看更新结果

我看到你把答案改为只使用java，但我希望这能对你有所帮助

Answer 4

在PHP中非常简单，可以使用fgetcsv函数http://php.net/manual/en/function.fgetcsv.php

添加样本

    <?php

    $inHandle= fopen("input.csv", "r");

    $text = "";
    $someVar = array(1, 2, 3, 4);           // for subtracting 1 from col1 2 from col2 ...

    while ( ( $data = fgetcsv($inHandle) ) !== FALSE) 
    {
    $text  = $text  . $data[0];

    for ($i= 1; $i < count($data);  $i++) 
    {

        if($i==0)
            $text =  $text .  $data[$i] . ", ";
        else
            $text =  $text .  ( $data[$i] - $someVar[$i -1] ) . " , ";
    }
       $text =  $text . " \n";
    }

    fclose($inHandle);

    $outHandle = fopen('output.csv', 'w');

    fwrite($outHandle , $text );

    fclose($outHandle );
    ?>

Answer 5

据我所知，没有“简单”的方法可以做到这一点，至少在标准JavaAPI中是这样。循环可能是这里唯一的选择

然而，还有其他语言使这类事情相对简单。R（免费提供且开源）是一种用于数据操作的优秀语言

Answer 6

您可能对我发布到GitHub的代码感兴趣，它读取CSV，将CSV放入POJO，然后从POJO写入CSV文件。这将使用POJO修改原始CSV，并将所需的新列写入新的CSV文件

https://github.com/Blue4570/CsvAppender

公共类CsvWriter{

private File csvFile;
private String delimiter;
static final String NEW_FILE_LOCATION_AND_NAME = "<LOCATION_AND_NAME_OF_YOUR_FILE_HERE";


public CsvWriter(String delimiter) {
    this.csvFile = new File(getClass().getClassLoader().getResource("csv/TestCsv.txt").getFile());
    this.delimiter = delimiter;
}

public void writeFile() {
    List<NewTable> tableList = readFile(csvFile);
    try(FileWriter writer = new FileWriter(NEW_FILE_LOCATION_AND_NAME)) {
        writer.append("ID$FirstName$LastName").append("\n");
        tableList.forEach(table -> {
            try {
                writer.append(table.getId()).append(delimiter);
                writer.append(table.getFirstName()).append(delimiter);
                writer.append(table.getLastName());
                writer.append("\n");
            } catch (IOException e) {
                System.out.println("Unable to write new File");
                e.printStackTrace();
            }
        });
    } catch(IOException e) {
        System.out.println("Unable to write new file");
    }
}

private List<NewTable> readFile(File csvFile) {
    List<NewTable> tableList = new ArrayList<>();
    try (InputStream inputFS = new FileInputStream(csvFile);
         BufferedReader br = new BufferedReader(new InputStreamReader(inputFS))
    ) {
        // skip the header of the csv
        tableList = br.lines().skip(1).map(mapToItem).collect(Collectors.toList());

    } catch (IOException e) {
        System.out.println("Error reading file");
    }
    return tableList;
}

private Function<String, NewTable> mapToItem = (line) -> {
    Optional<NewTable> newTable = Optional.empty();
    if (line != null) {
        String[] p = line.split("\\$");
         newTable = Optional.of(new NewTable(p[0], p[1]));
    }
    return newTable.orElseGet(NewTable::new);
};

}