用JAVA实现对.txt文件的读取与写入

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.io.*;
import java.util.*;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) throws IOException {
//        SpringApplication.run(DemoApplication.class, args);
        Map<Integer, String> read = readTxtFile("D:\\data\\list.txt");
        List<String> strings = new ArrayList<>(1000);//初始容量为1000
        final Iterator<Integer> iterator = read.keySet().iterator();//keySet()返回值，所有key；iterator()遍历
        //当在缓冲区内扫描到字符时，会返回true， 否则会发生阻塞，等待数据输入。
        //hasNext("World")匹配到对应字符返回true，
        while (iterator.hasNext()){
             Integer key = iterator.next();
             String s = read.get(key);
            System.out.println(s);
            strings.add(s);

        }
        writeTxtFile("D:\\data\\list1.txt",strings);


    }
    private static Map<Integer,String> readTxtFile(String filePath){
        Map<Integer, String> txtMap = new HashMap<Integer,String>(1000);//<key,value>
        try(FileInputStream fileInputStream = new FileInputStream(filePath);//从文件系统中的某个文件中获得输入字节
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);//创建一个使用默认字符集的 InputStreamReader。字节转换为字符
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);)//缓存区 BufferReader类用来包装所有其 read() 操作可能开销很高的 Reader（如 FileReader 和InputStreamReader）。
        {
            String line = null;
            Integer i = 0;
            while ((line =bufferedReader.readLine())!=null){//readline() 方法用于从文件读取整行,包括 “\n” 字符
                i=i+1;
                txtMap.put(i,line);
            }
        }
        catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }return txtMap;

    }
    private static void writeTxtFile(String filePath,List<String> textList)throws IOException{
        final File file = new File(filePath);//通过给定的父抽象路径名和子路径名字符串创建一个新的File实例
        file.createNewFile();
        try(FileWriter fileWriter =new FileWriter(file);//字符向流中写入数据
            final BufferedWriter bufferedWriter = new BufferedWriter(fileWriter)){//BufferedWriter加入了缓冲技术,将字符读取对象作为参数
            for (String text:textList){//循环textList赋值给text
                bufferedWriter.write(text);//text写入
                bufferedWriter.newLine();//使用自己的行分隔符概念
            }
            bufferedWriter.flush();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

}