將文檔的內容排序：

public static void main(String[] args) throws IOException {File dir = new File("J:\\360downloads\\wpcache\\srvsetwp\\xxx\\test.txt");BufferedReader br = new BufferedReader(new FileReader(dir));//把按行讀取到的內容，把文件中所有行分別放到ArrayList中ArrayList<String> list = new ArrayList<>();while (true){String line = br.readLine();if (line == null){break;}list.add(line);}//關閉流br.close();//按照首行第一個字符大小重新排序，調用Arraylist自帶的排序方法list.sort((o1, o2) -> o1.charAt(0) - o2.charAt(0));//將排好的順序寫入到文件中BufferedWriter bw = new BufferedWriter(new FileWriter(dir));for (String s : list) {bw.write(s);bw.newLine();}//關閉流bw.close();}