89. 在下列程序的空白处，应填入的正确选项是______。
import java.io.*;
public class ObjectStreamTest{
public static void main(String args[]) throws IOException {
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("serial.bin"));
java.util.Date d = new java.util.Date();
oos.______(d);
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("serial.bin"));
try{
java.util.Date restoredDate = (java.util.Date) ois.readObject();
System.out.println("read Object back from serial.bin file: "+restoredDate);
}
catch(ClassNotFoundException cnf) {
System.out.println("class not found");
}
}
}
