java怎么合并在指定目录上的两个文件,放在一个新的文件中

import java.io.*;public class Api {    public static void main(String[] args) throws Exception {        File f = new File("D:\\test");// 目录        FileReader fr = null;        BufferedReader br = null;        File fwrite = new File("D:\\ALLCDR.TXT");// 文件        FileWriter fw = new FileWriter(fwrite);// 写文件流        File[] fall = f.listFiles();        for (int count = 0; count < fall.length; count++) {            fr = new FileReader(fall[count]);            br = new BufferedReader(fr);            String str = br.readLine();            while (str != null) {                System.out.println(str);                fw.write(str + "\n");                fw.flush();                str = br.readLine();            }            br.close();            fr.close();        }        fw.close();    }}