public static void copyFile(File srcFile,File destFile)throws IOException{
  if(!srcFile.exists()){
   throw new IllegalArgumentException("文件"+srcFile+"不存在");
  }
  if(!srcFile.isFile()){
   throw new IllegalArgumentException(srcFile+"不是文件");
  }
  FileInputStream in=new FileInputStream(srcFile);
  FileOutputStream out=new FileOutputStream(destFile);
  byte[] buf=new byte[8*1024];
  int b;
  while((b=in.read(buf,0,buf.length))!=-1){
   out.write(buf,0,b);
   out.flush();
  }
  in.close();
  out.close();
 }

public static void main(String[] args) throws IOException {
  // TODO Auto-generated method stub
  try{
  IOUtil.copyFile(new File("C:\\2345下载\\Test1.java"), new File(
    "C:\\2345下载"));
  }catch (IOException e) {
   // TODO: handle exception
   e.printStackTrace();
  }
 }

java.io.FileNotFoundException: C:\2345下载 (拒绝访问。)
 at java.io.FileOutputStream.open(Native Method)
 at java.io.FileOutputStream.<init>(FileOutputStream.java:179)
 at java.io.FileOutputStream.<init>(FileOutputStream.java:131)
 at package1.IOUtil.copyFile(IOUtil.java:62)
 at package1.IOUtilTest3.main(IOUtilTest3.java:15)