javamail接收邮件，解析时乱码，想转回去怎么转呢

我的源代码：
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.mail.BodyPart;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.Part;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.internet.MimeUtility;

public class RecevieMailDemo3 {

public static void main(String args[]) throws Exception {
Properties props = System.getProperties();

Session session = Session.getDefaultInstance(props);

Store store = session.getStore("pop3");
store.connect("pop3.sohu.com", "xxxxxxxxxxx", "xxxxxxxxxxxx");

Folder folder = store.getFolder("INBOX");
folder.open(Folder.READ_ONLY);

Message[] messages = folder.getMessages();

for (Message msg:messages) {
String contentType = msg.getContentType();

if (msg.isMimeType("text/plain")) {
System.out.println(msg.getContent());

} else if (msg.isMimeType("multipart/mixed")){
Multipart multipart = (Multipart)msg.getContent();
int count = multipart.getCount();
// System.out.println(count);
for (int i=0;i<count;i++) {
BodyPart bodyPart = multipart.getBodyPart(i);
String disposition = bodyPart.getDisposition();
System.out.println(bodyPart.getContentType()+i);
if (disposition !=null && disposition.equals(Part.ATTACHMENT)) {
System.out.println("ATTACHMENT");
DataHandler dataHandler = bodyPart.getDataHandler();
String name = MimeUtility.decodeText(dataHandler.getName());
InputStream is = dataHandler.getInputStream();
OutputStream os = new FileOutputStream("D:/temp/"+name);
byte[] bytes = new byte[1024];
while (is.read(bytes)!=-1) {
os.write(bytes);
}
System.out.println(name+i);
} else if (bodyPart.isMimeType("multipart/related")){
System.out.println(((Multipart)bodyPart.getContent()).getBodyPart(0).getContent()+"***content***"+i);
InputStream is = bodyPart.getInputStream();
OutputStream os = new FileOutputStream("d:/temp/demo3.html");
byte []bytes = new byte[1024];
while(is.read(bytes)!=-1) {
os.write(bytes);
}
os.flush();
is.close();
os.close();
} }
} else if (msg.isMimeType("text/html")) {
InputStream is = msg.getInputStream();
OutputStream os = new FileOutputStream("d:/temp/demo3.mht");
byte b[] = new byte[1024];
while (is.read(b) != -1) {
os.write(b);
}
os.flush();
is.close();
os.close();
System.out.println("HTMLHTMLHTMLHTMLHTMLHTMLHTMLHTML");
}
}
}
}




写入html的邮件的内容：------=_=BF=A7=E0=AC=BB=CA=B9=AC=B6=ED=BA=A3=B9=D8=C0=B1=BB=F0=B9=F8=B0=A2=C0=EF=B9=

=FD=BA=F3=DA=C0=D2=BB=B8=F6=C4=C7=B8=F6=C0=AD=B8=F1=BA=CD=B0=A2=B8=E7=B9=FE=

=B9=FE=B8=F6=C0=AC=BB=F8=B9=DC=C0=ED=B8=F6=C5=B6=CE=D2=D2=BB=B9=B2=D2=AA=B7= 就是类似于这样的BASE64编码，该怎样把base64编码转回去呢