写文件文件问题！

[alemjann]

可以生成文件，但是文件没有内容，请大家指点！谢谢。
/************************************/

package fwrite;

import java.io.*;

public class FWriter {
public FWriter(String content) throws IOException
{
System.out.println(content);
String file_path = "file/";
String root = "d:/";
String file_name = "aaa.txt";
File file = new File(root + File.separator + file_path + File.separator + file_name);
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(file)));
pw.write(content);
}

public static void main(String[] args) {
try
{
FWriter fwr = new FWriter("hello file!");
}
catch(IOException ioe)
{
System.out.println(ioe.toString());
}
}
}

[lotofu]

pw.write(content);//之后，加上
pw.flush();
pw.close();