以下是编写文件的代码，也在退出帮助内容网页时删除：

public String writeHelpContent(String filePath, String helpPageContent) throws IOException{
        logger.info("HowToUseRiskOfficeHelpService - writeHelpContent start");
        File file = new File(filePath);
        try(FileWriter fw = new FileWriter(file);){
            file.deleteOnExit();
            if(file.createNewFile()) {
                logger.info("HowToUseRiskOfficeHelpService - file created successfully");
            }else {
                logger.info("HowToUseRiskOfficeHelpService - file already exists");
            }
            fw.write(helpPageContent); 
            fw.flush();
        }

        return "Sucessfully write into help page file";
    }

如果您已经有了要写入文件的内容（而不是动态生成的），那么Java7中作为本机I/O的一部分添加的java.nio.file.Files提供了实现目标的最简单、最有效的方法。

基本上，创建和写入文件只需一行，而且只需一个简单的方法调用！

以下示例创建并写入6个不同的文件，以展示如何使用它：

Charset utf8 = StandardCharsets.UTF_8;
List<String> lines = Arrays.asList("1st line", "2nd line");
byte[] data = {1, 2, 3, 4, 5};

try {
    Files.write(Paths.get("file1.bin"), data);
    Files.write(Paths.get("file2.bin"), data,
            StandardOpenOption.CREATE, StandardOpenOption.APPEND);
    Files.write(Paths.get("file3.txt"), "content".getBytes());
    Files.write(Paths.get("file4.txt"), "content".getBytes(utf8));
    Files.write(Paths.get("file5.txt"), lines, utf8);
    Files.write(Paths.get("file6.txt"), lines, utf8,
            StandardOpenOption.CREATE, StandardOpenOption.APPEND);
} catch (IOException e) {
    e.printStackTrace();
}

有一些简单的方法，例如：

File file = new File("filename.txt");
PrintWriter pw = new PrintWriter(file);

pw.write("The world I'm coming");
pw.close();

String write = "Hello World!";

FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);

fw.write(write);

fw.close();

请注意，下面的每个代码示例都可能引发IOException。为了简洁起见，省略了Try/catch/finally块。有关异常处理的信息，请参阅本教程。

请注意，如果文件已经存在，下面的每个代码示例都将覆盖该文件

创建文本文件：

PrintWriter writer = new PrintWriter("the-file-name.txt", "UTF-8");
writer.println("The first line");
writer.println("The second line");
writer.close();

创建二进制文件：

byte data[] = ...
FileOutputStream out = new FileOutputStream("the-file-name");
out.write(data);
out.close();

Java 7+用户可以使用Files类写入文件：

创建文本文件：

List<String> lines = Arrays.asList("The first line", "The second line");
Path file = Paths.get("the-file-name.txt");
Files.write(file, lines, StandardCharsets.UTF_8);
//Files.write(file, lines, StandardCharsets.UTF_8, StandardOpenOption.APPEND);

创建二进制文件：

byte data[] = ...
Path file = Paths.get("the-file-name");
Files.write(file, data);
//Files.write(file, data, StandardOpenOption.APPEND);

我认为这是最短的路：

FileWriter fr = new FileWriter("your_file_name.txt"); // After '.' write
// your file extention (".txt" in this case)
fr.write("Things you want to write into the file"); // Warning: this will REPLACE your old file content!
fr.close();

最好的方法是使用Java7：Java7引入了一种处理文件系统的新方法，以及一个新的实用程序类—Files。使用Files类，我们还可以创建、移动、复制、删除文件和目录；它还可以用于读取和写入文件。

public void saveDataInFile(String data) throws IOException {
    Path path = Paths.get(fileName);
    byte[] strToBytes = data.getBytes();

    Files.write(path, strToBytes);
}

使用FileChannel写入如果您正在处理大型文件，FileChannel可以比标准IO更快。以下代码使用FileChannel将字符串写入文件：

public void saveDataInFile(String data) 
  throws IOException {
    RandomAccessFile stream = new RandomAccessFile(fileName, "rw");
    FileChannel channel = stream.getChannel();
    byte[] strBytes = data.getBytes();
    ByteBuffer buffer = ByteBuffer.allocate(strBytes.length);
    buffer.put(strBytes);
    buffer.flip();
    channel.write(buffer);
    stream.close();
    channel.close();
}

使用DataOutputStream写入

public void saveDataInFile(String data) throws IOException {
    FileOutputStream fos = new FileOutputStream(fileName);
    DataOutputStream outStream = new DataOutputStream(new BufferedOutputStream(fos));
    outStream.writeUTF(data);
    outStream.close();
}

使用FileOutputStream写入

现在让我们看看如何使用FileOutputStream将二进制数据写入文件。以下代码转换String int字节，并使用FileOutputStream将字节写入文件：

public void saveDataInFile(String data) throws IOException {
    FileOutputStream outputStream = new FileOutputStream(fileName);
    byte[] strToBytes = data.getBytes();
    outputStream.write(strToBytes);

    outputStream.close();
}

使用PrintWriter写入我们可以使用PrintWriter将格式化文本写入文件：

public void saveDataInFile() throws IOException {
    FileWriter fileWriter = new FileWriter(fileName);
    PrintWriter printWriter = new PrintWriter(fileWriter);
    printWriter.print("Some String");
    printWriter.printf("Product name is %s and its price is %d $", "iPhone", 1000);
    printWriter.close();
}

使用BufferedWriter写入：使用BufferedWriter将字符串写入新文件：

public void saveDataInFile(String data) throws IOException {
    BufferedWriter writer = new BufferedWriter(new FileWriter(fileName));
    writer.write(data);

    writer.close();
}

将字符串附加到现有文件：

public void saveDataInFile(String data) throws IOException {
    BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
    writer.append(' ');
    writer.append(data);

    writer.close();
}