将d盘下的xxx.jar(200M左右)文件复制到e盘下 1、 利用输入输出流完成文件的复制 2、 利用缓冲输入输出流完成文件的复制 3、 对比速度

好的，这是一个关于文件复制的问题，我可以帮你解答。这里提供三种实现方式：

1. 利用输入输出流完成文件复制

import java.io.*;

public class CopyFile {

    public static void main(String[] args) {
        String sourcePath = "D:/xxx.jar";
        String targetPath = "E:/xxx.jar";

        try (InputStream in = new FileInputStream(sourcePath);
             OutputStream out = new FileOutputStream(targetPath)) {
            byte[] buffer = new byte[1024];
            int len;
            while ((len = in.read(buffer)) > 0) {
                out.write(buffer, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. 利用缓冲输入输出流完成文件复制

import java.io.*;

public class CopyFileBuffered {

    public static void main(String[] args) {
        String sourcePath = "D:/xxx.jar";
        String targetPath = "E:/xxx.jar";

        try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(sourcePath));
             BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(targetPath))) {
            byte[] buffer = new byte[1024];
            int len;
            while ((len = in.read(buffer)) > 0) {
                out.write(buffer, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. 对比速度

我们可以使用Java自带的System.currentTimeMillis()方法来计算复制时间，然后比较两种方式的时间差异。

import java.io.*;

public class CopyFile {

    public static void main(String[] args) {
        String sourcePath = "D:/xxx.jar";
        String targetPath = "E:/xxx.jar";

        try (InputStream in = new FileInputStream(sourcePath);
             OutputStream out = new FileOutputStream(targetPath)) {
            byte[] buffer = new byte[1024];
            int len;
            long start = System.currentTimeMillis();
            while ((len = in.read(buffer)) > 0) {
                out.write(buffer, 0, len);
            }
            long end = System.currentTimeMillis();
            System.out.println("普通IO复制时间：" + (end - start) + "ms");
        } catch (IOException e) {
            e.printStackTrace();
        }

        try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(sourcePath));
             BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(targetPath))) {
            byte[] buffer = new byte[1024];
            int len;
            long start = System.currentTimeMillis();
            while ((len = in.read(buffer)) > 0) {
                out.write(buffer, 0, len);
            }
            long end = System.currentTimeMillis();
            System.out.println("缓冲IO复制时间：" + (end - start) + "ms");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

通过测试可以发现，使用缓冲输入输出流复制文件的速度比使用普通输入输出流快。