io流练习题，字符的输入输出流

问题遇到的现象和发生背景

20. 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

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！