io流练习题，字符的输入输出流

Question

问题遇到的现象和发生背景

1. 用缓冲字节流实现文件复制的功能
   创建a.txt文件，然后把a.txt文件复制成acopy.txt
   a.txt文件中的内容未能成功复制到acopy.txt中，acopy.txt中为空白

   用代码块功能插入代码，请勿粘贴截图

   @Test
   public void test5() {

   BufferedReader br = null;
   BufferedWriter bw = null;
   BufferedWriter bw1 = null;
   try {
       bw1 = new BufferedWriter(new FileWriter("d:\\c.txt"));
       bw1.write("dasdsadadadsllll");
   
       br = new BufferedReader(new FileReader("d:\\c.txt"));
       bw = new BufferedWriter(new FileWriter("d:\\copy4.txt"));
       int len;
       char[] cbuf=new char[5];
       while ((len=br.read(cbuf))!=-1){
           bw.write(cbuf,0,len);
       }
   } catch (IOException e) {
       e.printStackTrace();
   } finally {
       if(bw!=null){
           try {
               bw.close();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
       if(br!=null){
           try {
               br.close();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
       if(bw1!=null){
           try {
               bw1.close();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   }
   

}

运行结果及报错内容

无法成功复制内容

Answer 1

我帮你修改了下：直接运行测试即可，写入流结束后，得先关闭流。

package cn.personal.demo07;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class Test5 {
    public static void main(String[] args) {

        BufferedReader br = null;
        BufferedWriter bw = null;
        BufferedWriter bw1 = null;
        try {
            bw1 = new BufferedWriter(new FileWriter("d:\\c.txt"));
            bw1.write("dasdsadadadsllll");
            bw1.close();
            br = new BufferedReader(new FileReader("d:\\c.txt"));
            
            bw = new BufferedWriter(new FileWriter("d:\\copy4.txt"));
            int len;
            while ((len = br.read()) != -1) {
                bw.write(len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bw != null) {
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bw1 != null) {
                try {
                    bw1.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

答题不易，还请采纳！