Java 使用换行符读取和写入.csv文件

我有一个.csv文件，如下所示：

Col1,Col2,Col3,Col4,Col5
1,2,3,4,5

//Read stream
File myFile = new File("C:\\testFile.csv");
InputStreamReader isTest = new InputStreamReader(myStream);
StringBuilder sbTest = new StringBuilder();
BufferedReader brTest = new BufferedReader(isTest );
String readTest = brTest.readLine();

while(readTest != null) {
    sbTest .append(readTest);
    readTest = brTest.readLine();
}

//Write stream

FileWriter fwTest = new FileWriter(myFile .getAbsoluteFile());
BufferedWriter bwTest = new BufferedWriter(fwTest);

bwTest .write(sbTest.toString());
bwTest .close();

private static final String NEWLINE = System.getProperty("line.separator");

我正在做这样的事情：

Col1,Col2,Col3,Col4,Col5
1,2,3,4,5

//Read stream
File myFile = new File("C:\\testFile.csv");
InputStreamReader isTest = new InputStreamReader(myStream);
StringBuilder sbTest = new StringBuilder();
BufferedReader brTest = new BufferedReader(isTest );
String readTest = brTest.readLine();

while(readTest != null) {
    sbTest .append(readTest);
    readTest = brTest.readLine();
}

//Write stream

FileWriter fwTest = new FileWriter(myFile .getAbsoluteFile());
BufferedWriter bwTest = new BufferedWriter(fwTest);

bwTest .write(sbTest.toString());
bwTest .close();

private static final String NEWLINE = System.getProperty("line.separator");

但是，当我打开文件时，我会看到以下CSV：

Col1,Col2,Col3,Col4,Col51,2,3,4,5

---

有没有办法解析换行符并确保在写入文件时追加换行符？

看起来您需要做的就是将换行符追加到StringBuilder中。要使其独立于平台，请使用系统的line.separator属性，如下所示：

sbTest.append(readTest).append(System.getProperty("line.separator"));

将字符串写入BufferWriter时，对该字符串调用

trim（）

，以删除悬空换行符

bwTest.write(sbTest.toString().trim());

---

正如dkatzel所建议的，您可能还希望将行分隔符设置为常量。大概是这样的：

Col1,Col2,Col3,Col4,Col5
1,2,3,4,5

//Read stream
File myFile = new File("C:\\testFile.csv");
InputStreamReader isTest = new InputStreamReader(myStream);
StringBuilder sbTest = new StringBuilder();
BufferedReader brTest = new BufferedReader(isTest );
String readTest = brTest.readLine();

while(readTest != null) {
    sbTest .append(readTest);
    readTest = brTest.readLine();
}

//Write stream

FileWriter fwTest = new FileWriter(myFile .getAbsoluteFile());
BufferedWriter bwTest = new BufferedWriter(fwTest);

bwTest .write(sbTest.toString());
bwTest .close();

private static final String NEWLINE = System.getProperty("line.separator");

然后，while循环将包括以下内容：

sbTest.append(readTest).append(NEWLINE);

---

什么是您的

myStream

？您需要在将行引入

sbTest

时添加换行符。我不确定您是否要使用stringbuilder。否则，您希望在每个appendmyStream都是.csv文件之后添加换行符。如果您没有定义

myStream

，您是如何运行程序的？最好将属性值作为常量取出，因为您只需查找一次。