Java中的图片如何利用 IO中字节流进行复制

package learn;import java.io.*;public class Learn{  public static void main(String[] args) throws IOException {    File file1=new File("D:/a.jpg");    File file2=new File("D:/b.jpg");    byte[] b=new byte[(int)file1.length()];    FileInputStream in=null;    FileOutputStream out=null;    try {      in=new FileInputStream(file1);      out=new FileOutputStream(file2);//没有指定文件则会创建      while(in.read(b)!=-1){    //read()--int，-1表示读取完毕        out.write(b);      }      out.flush();      in.close();      out.close();    } catch (FileNotFoundException e) {      e.printStackTrace();    }  }}