复制Jar包时少了META-INFO/MANIFEST.MF

Question

用如下代码将工程目录中的res\test.jar复制到D:\Test下，发现System.out.println(entry.getName())没有输出“META-INFO/MANIFEST.MF”这项，在D:\Test\test.jar中，其它的JarEntry都复制过来了，就是少了"META-INFO"文件夹和该文件夹下的.MF文件。请问这是怎么回事呢??谢谢....
public static void jarCopy_JarEntry() {
try {
JarInputStream jarIn = new JarInputStream(new FileInputStream(
"res//test.jar"));
JarOutputStream jarOut = new JarOutputStream(new FileOutputStream(
"D://Test//test.jar"));
byte[] buf = new byte[4096];
JarEntry entry;
while ((entry = jarIn.getNextJarEntry()) != null) {
System.out.println(entry.getName());
jarOut.putNextEntry(entry);
int read;
while ((read = jarIn.read(buf)) != -1) {
jarOut.write(buf, 0, read);
}
jarOut.closeEntry();
}
jarOut.flush();
jarOut.close();
jarIn.close();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("OK");
}

Answer 1

 public static void jarCopy_JarEntry() {
        try {
            JarInputStream jarIn = new JarInputStream(new FileInputStream(
                    "D:\\jacob.jar"));
            Manifest manifest = jarIn.getManifest();//manifest.......
            JarOutputStream jarOut;
            if(manifest != null) {
             jarOut = new JarOutputStream(new FileOutputStream(
             "D:\\jacob2.jar"),manifest);
            
            }else {
             jarOut = new JarOutputStream(new FileOutputStream(
             "D:\\jacob2.jar"));
            }
            
            byte[] buf = new byte[4096];
            JarEntry entry;
            
            while ((entry = jarIn.getNextJarEntry()) != null) {
                System.out.println(entry.getName());
                jarOut.putNextEntry(entry);
                int read;
                while ((read = jarIn.read(buf)) != -1) {
                    jarOut.write(buf, 0, read);
                }
                jarOut.closeEntry();
            }
            
            
            jarOut.flush();
            jarOut.close();
            jarIn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("OK");
    }

Answer 2

JarOutputStream
public JarOutputStream(OutputStream out)
                throws IOException
Creates a new JarOutputStream with no manifest. 
JarOutputStream
public JarOutputStream(OutputStream out,
                       Manifest man)
                throws IOException
Creates a new JarOutputStream with the specified Manifest. The manifest is written as the first entry to the output stream. 
明白了，谢谢...