Java中读取一个TXT文件中的每行内容的前5个字符，并保存到另一个TXT文件中。

曾经的一道面试题：读取一个文件“员工信息.txt”, 取每行内容的前5个字符，存储到“员工姓名.txt”文件中。

方法一：

package test01;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.List;

public class FileTest {
    private List list = new ArrayList();
    private String temp;

    public static void main(String[] args) {
        FileTest fileTest = new FileTest();
        fileTest.readFile("E:/work/a.txt");
        fileTest.printFile("E:/work/b.txt");
        System.out.println(fileTest.list);
    }

    public void readFile(String fileName) {
        try {
            FileReader fileReader = new FileReader(new File(fileName));
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            while ((temp = bufferedReader.readLine()) != null) {
                list.add(temp);
            }
            bufferedReader.close();
            fileReader.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void printFile(String fileName) {

        try {
            FileWriter fileWriter = new FileWriter(new File(fileName));
            BufferedWriter bufWriter = new BufferedWriter(fileWriter);
            for (int i = 0; i < list.size(); i++) {
                bufWriter.write(list.get(i), 0, 5);//读取前5个字符
                bufWriter.newLine();
            }
            bufWriter.close();
            fileWriter.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

方法二：

package test01;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.List;

public class ReadFile03 {

    public static void main(String[] args) {
        List list = new ArrayList<>();
        String s = null;
        File f1 = new File("E:/work/员工信息.txt");//员工信息中要有员工数据
        File f2 = new File("E:/work/员工姓名.txt");

        try {
            // 读取“员工信息.txt”文件
            FileReader fileReader = new FileReader(f1);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            while ((s = bufferedReader.readLine()) != null) {
                list.add(s);
            }
            System.out.println(list);// 打印list中读到的数据

            // 写入“员工姓名.txt”文件
            FileWriter fileWriter = new FileWriter(f2);
            BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
            for (int i = 0; i < list.size(); i++) {
                bufferedWriter.write(list.get(i), 0, 5);// 截取前5个字符
                bufferedWriter.newLine();
            }

            // 关闭流
            bufferedReader.close();
            fileReader.close();
            bufferedWriter.close();
            fileWriter.close();

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}