一.原文件 

二.代码

package org.example;

import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class day12 {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("d:/temp/day05/出师表.txt"));
             BufferedWriter bf = new BufferedWriter(new FileWriter("d:/temp/day05/新出师表.txt"))
        ) {
            //定义ArrayList集合存储内容
            List<String> data = new ArrayList<>();
            //按行读取
            String line;
            while ((line = br.readLine()) != null) {
                data.add(line);
            }
            //排序
            Collections.sort(data);
            System.out.println(data);
            //遍历集合内容，写出到新文件
            for (String s : data) {
                bf.write(s);
                bf.newLine();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

三.结果