在Java教程中，Java文件讀寫的方法是最基礎的課程。

使用 FileReader 和 FileWriter 讀寫

讓我們從使用FileReader和FileWriter類開始：

String directory = System.getProperty("user.home");
String fileName = "sample.txt";
String absolutePath = directory + File.separator + fileName;
// Write the content in file 
try(FileWriter fileWriter = new FileWriter(absolutePath)) {
    String fileContent = "This is a sample text.";
    fileWriter.write(fileContent);
    fileWriter.close();
} catch (IOException e) {
    // Cxception handling
}
// Read the content from file
try(FileReader fileReader = new FileReader(absolutePath)) {
    int ch = fileReader.read();
    while(ch != -1) {
        System.out.print((char)ch);
        fileReader.close();
    }
} catch (FileNotFoundException e) {
    // Exception handling
} catch (IOException e) {
    // Exception handling
}

這兩個類都接受一個字符串，在它們的構造函數中表示文件的路徑。您還可以傳遞一個File對象以及一個FileDescriptor.

該write()方法寫入一個有效的字符序列 - a String， a char[]。此外，它可以編寫一個char表示為int.

該read()方法逐個字符地讀取并返回，while例如，允許我們在循環中使用讀取的數據。

不要忘記在使用后關閉這兩個類!

使用 BufferedReader 和 BufferedWriter 讀寫

使用BufferedReader和BufferedWriter類：

String directory = System.getProperty("user.home");
String fileName = "sample.txt";
String absolutePath = directory + File.separator + fileName;
// Write the content in file 
try(BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(absolutePath))) {
    String fileContent = "This is a sample text.";
    bufferedWriter.write(fileContent);
} catch (IOException e) {
    // Exception handling
}
// Read the content from file
try(BufferedReader bufferedReader = new BufferedReader(new FileReader(absolutePath))) {
    String line = bufferedReader.readLine();
    while(line != null) {
        System.out.println(line);
        line = bufferedReader.readLine();
    }
} catch (FileNotFoundException e) {
    // Exception handling
} catch (IOException e) {
    // Exception handling
}

使用 FileInputStream 和 FileOutputStream 讀寫

使用FileInputStream和FileOutputStream類：

String directory = System.getProperty("user.home");
String fileName = "sample.txt";
String absolutePath = directory + File.separator + fileName;
// write the content in file 
try(FileOutputStream fileOutputStream = new FileOutputStream(absolutePath)) {
    String fileContent = "This is a sample text.";
    fileOutputStream.write(fileContent.getBytes());
} catch (FileNotFoundException e) {
    // exception handling
} catch (IOException e) {
    // exception handling
}
// reading the content of file
try(FileInputStream fileInputStream = new FileInputStream(absolutePath)) {
    int ch = fileInputStream.read();
    while(ch != -1) {
        System.out.print((char)ch);
        ch = fileInputStream.read();
    }
} catch (FileNotFoundException e) {
    // exception handling
} catch (IOException e) {
    // exception handling
}

使用 BufferedInputStream 和 BufferedOutputStream 進行讀寫

使用BufferedInputStream和BufferedOutputStream類：

String directory = System.getProperty("user.home");
String fileName = "sample.txt";
String absolutePath = directory + File.separator + fileName;
// write the content in file 
try(BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(absolutePath))) {
    String fileContent = "This is a sample text.";
    bufferedOutputStream.write(fileContent.getBytes());
} catch (IOException e) {
    // exception handling
}
// read the content from file
try(BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(absolutePath))) {
    int ch = bufferedInputStream.read();
    while(ch != -1) {
        System.out.print((char)ch);
        ch = bufferedInputStream.read();
    }
} catch (FileNotFoundException e) {
    // exception handling
} catch (IOException e) {
    // exception handling
}

使用 Java.nio 類讀寫

使用java.nio類：

String directory = System.getProperty("user.home");
String fileName = "sample.txt";
String content = "This is a sample text.";
Path path = Paths.get(directory, fileName);
try {
    Files.write(path, content.getBytes(), StandardOpenOption.CREATE);
} catch (IOException e) {
    // exception handling
}
try {
    List<String> list = Files.readAllLines(path);
    list.forEach(line -> System.out.println(line));
} catch (IOException e) {
    // exception handling
}

另一種通過Files類檢索內容的方法(如果您不讀取文本數據則更重要)是使用該readAllBytes方法將數據讀入字節數組：

try { 
    byte[] data = Files.readAllBytes(path);
    System.out.println(new String(data));
} catch (IOException e) {
    // exception handling
}

如果您有興趣使用帶有的流java.nio，您還可以使用該類提供的以下方法Files：

Files.newBufferedReader(path)
Files.newBufferedWriter(path, options)
Files.newInputStream(path, options)
Files.newOutputStream(path, options)