要將Java生成的數據存入文件，可以使用Java的文件輸入輸出流（FileInputStream和FileOutputStream）或者使用Java的文件寫入器（FileWriter）來實現。

使用文件輸入輸出流的示例代碼如下：

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileExample {
    public static void main(String[] args) {
        String data = "Hello, World!";
        String filename = "output.txt";

        try {
            FileOutputStream outputStream = new FileOutputStream(filename);
            outputStream.write(data.getBytes());
            outputStream.close();
            System.out.println("Data has been written to the file.");
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            FileInputStream inputStream = new FileInputStream(filename);
            int content;
            while ((content = inputStream.read()) != -1) {
                System.out.print((char) content);
            }
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用文件寫入器的示例代碼如下：

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterExample {
    public static void main(String[] args) {
        String data = "Hello, World!";
        String filename = "output.txt";

        try {
            FileWriter writer = new FileWriter(filename);
            writer.write(data);
            writer.close();
            System.out.println("Data has been written to the file.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

以上兩個示例代碼都會將字符串"Hello, World!"寫入名為"output.txt"的文件中。