java - 无法写入 java 中的文件，因为它正在使用 System.out.println 打印

Question

File output=new File("C:\\\\MDU-1617-CSJ0098\\\\web\\\\products.txt");
BufferedWriter writer1 = new BufferedWriter(new FileWriter(output));               
while(q_set2.next()) {
    String s = String.valueOf(q_set2.getInt(1));
    System.out.print(s);
    writer1.write(s);
    writer1.newLine();
}

输出是运行:123456 构建成功(总时间:0 秒)

但是文件中没有数据

Answer 1

This write 方法的作用是:

Ordinarily this method stores characters from the given array into this stream's buffer, flushing the buffer to the underlying stream as needed.

因此，它写入缓冲区而不是直接写入文件。要使缓冲区flush，您需要调用flush或close方法，例如:

File output = new File("C:\\\\MDU-1617-CSJ0098\\\\web\\\\products.txt");
BufferedWriter writer1 = new BufferedWriter(new FileWriter(output));
while (q_set2.next()) {
    String s = String.valueOf(q_set2.getInt(1));
    System.out.print(s);
    writer1.write(s);
    writer1.newLine();
}
writer1.close();

close() 在内部调用 flush()，因此，在这种情况下您不需要显式调用 flush() (这是Javadoc)。