JAVA对象所占字节大小计算方法

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;

/**
 * 
 * @version $Revision: 1.0 $ $Date:$
 * @author Yuriy Stepovoy. <ahref="mailto:[e-mail]">[e-mail]</a>
 **/

public class Utils {
    /**
     * 计算一个对象所占字节数
     * @param o对象，该对象必须继承Serializable接口即可序列化
     * @return
     * @throws IOException
     */
 public static int size(final Object o) throws IOException {
  if (o == null) {
   return 0;
  }
  ByteArrayOutputStream buf = new ByteArrayOutputStream(4096);
  ObjectOutputStream out = new ObjectOutputStream(buf);
  out.writeObject(o);
  out.flush();
  buf.close();

  return buf.size();
 }
    /**
     * 赋值对象，返回对象的引用，如果参数o为符合对象，则内部每一个对象必须可序列化
     * @param o对象，该对象必须继承Serializable接口即可序列化
     * @return
     * @throws IOException
     * @throws ClassNotFoundException
     */
 public static Object copy(final Object o) throws IOException,
   ClassNotFoundException {
  if (o == null) {
   return null;
  }

  ByteArrayOutputStream outbuf = new ByteArrayOutputStream(4096);
  ObjectOutput out = new ObjectOutputStream(outbuf);
  out.writeObject(o);
  out.flush();
  outbuf.close();

  ByteArrayInputStream inbuf = new ByteArrayInputStream(outbuf.toByteArray());
  ObjectInput in = new ObjectInputStream(inbuf);
  return in.readObject();
 }
}