java.io.NotSerializableException-联系人列表程序

嘿，我一直在努力让我的写和读方法发挥作用，但我不知道怎么了

除了这些方法不能正常工作之外，我还必须在TestDiskSaveing类中证明序列化工作正常。这就是为什么我把它设为null。 有什么想法吗

public class TestDiskSaving {

    public static void main(String args[]) {
        ContactList myList = new ContactList();
        myList.addContact();
        myList.addContact();
        myList.printAll();
        myList.find();

        myList.write();
        myList = null;
        System.out.println(myList);
        myList.read();
        System.out.println(myList);



    }
}

公共类联系人列表{
private ArrayList currentContacts=新建ArrayList（）；
/**
*在下一个未占用索引处将联系人添加到列表中
* 
*@作者尼克
*/
public void addContact（）{
currentContacts.add（newContact（））；
}
/**
*返回联系人列表的大小
* 
*@作者尼克
*/
公共int getSize（）{
返回currentContacts.size（）；
}
/**
*接受用户输入并返回新联系人
*/
私人联系人newContact（）{
扫描仪扫描=新扫描仪（System.in）；
System.out.println（“请输入此人的名字”）；
字符串newFirstName=scan.nextLine（）；
System.out.println（“请输入此人的姓氏”）；
字符串newLastName=scan.nextLine（）；
如果（！newLastName.trim（）.equals（null）&&！newLastName.trim（）.equals（“”）{
联系人联系人=新联系人（新姓氏）；
contact.setFirstName（newFirstName）；
System.out.println（“请输入此人的地址”）；
contact.setStreetAddress（scan.nextLine（））；
System.out.println（“请输入此人的电子邮件地址”）；
contact.setEmailAddress（scan.nextLine（））；
System.out.println（“请输入此人的电话号码”）；
contact.setPhoneNumber（scan.nextLine（））；
System.out.println（“请输入有关此人的任何其他附加信息”）；
contact.setNotes（scan.nextLine（））；
System.out.println（newFirstName+“”+newLastName+“已存储到联系人列表中”）；
返回联系人；
}否则{
System.out.println（“您没有输入此人的姓氏。”+“\n”
+“此人未被储存在联系人名单中。”）；
返回null；
}
}
/**
*按姓氏字母顺序打印列表中存储的所有联系人，然后
*名字。（不区分大小写）
* 
*@作者尼克
*/
public void printAll（）{
ArrayList打印列表=当前联系人；
Collections.sort（打印列表）；
对于（int i=0；i

公共类联系人实现可比较{
私有字符串名；
私有字符串lastName；
私有字符串streetAddress；
私有字符串电子邮件地址；
私有字符串电话号码；
私人弦乐；
/**
*设置联系人的姓氏
* 
*@作者阿曼
*/
公共联系人（字符串lastName）{
this.lastName=lastName；
}
/**
*返回联系人的姓氏
*@作者志祥
*/
公共字符串getLastName（）{
返回姓氏；
}
/**
*设置联系人的姓氏
*@作者尼克
*/
public void setLastName（字符串newLastName）{
this.lastName=newLastName；
}
/**
*打印出联系人上的所有数据，格式化后供用户查看。
*@作者志祥
*/
public void printInfo（）{
System.out.println（“名称：“+getFirstName（）+”+getLastName（））；
System.out.println（“Phone:+getPhoneNumber（））；
System.out.println（“地址：+getStreetAddress（））；
System.out.println（“Email:+getEmailAddress（））；
System.out.println（“Notes:+getNotes（））；
System.out.println（）；
}
/**
*返回联系人的名字
* 
* @
public class ContactList {
    private ArrayList<Contact> currentContacts = new ArrayList<Contact>();

    /**
     * Adds a contact to the list at the next unoccupied index
     * 
     * @author Nick
     */
    public void addContact() {
        currentContacts.add(newContact());
    }

    /**
     * returns the size of the contact list
     * 
     * @author Nick
     */
    public int getSize() {
        return currentContacts.size();
    }

    /**
     * take user input and return a new contact
     */
    private Contact newContact() {
        Scanner scan = new Scanner(System.in);
        System.out.println("Please enter the person's first name.");
        String newFirstName = scan.nextLine();

        System.out.println("Please enter the person's last name.");
        String newLastName = scan.nextLine();

        if (!newLastName.trim().equals(null) && !newLastName.trim().equals("")) {
            Contact theContact = new Contact(newLastName);
            theContact.setFirstName(newFirstName);

            System.out.println("Please enter the person's address.");
            theContact.setStreetAddress(scan.nextLine());

            System.out.println("Please enter the person's email address.");
            theContact.setEmailAddress(scan.nextLine());

            System.out.println("Please enter the person's phone number.");
            theContact.setPhoneNumber(scan.nextLine());

            System.out.println("Please enter any other additional information about the person.");
            theContact.setNotes(scan.nextLine());

            System.out.println(newFirstName + " " + newLastName + " got stored into the contact list");
            return theContact;
        } else {
            System.out.println("You did not enter the person's last name." + "\n"
                    + "The person did not get stored into the contact list.");
            return null;
        }

    }

    /**
     * Prints all contacts stored in the list, alphabetically by last name, then
     * first name. (not case sensitive)
     * 
     * @author Nick
     */
    public void printAll() {
        ArrayList<Contact> printList = currentContacts;
        Collections.sort(printList);
        for (int i = 0; i < printList.size(); i++) {
            printList.get(i).printInfo();
        }
    }

    /**
     * Find contact(s) in contact list by last name
     * 
     * @author Zhixiang
     */
    public void find() {
        Scanner scan = new Scanner(System.in);
        String lastName;
        System.out.println("Please enter a last name for search:");
        lastName = scan.nextLine();
        boolean found = false;
        for (int i = 0; i < currentContacts.size(); i++) {
            if (currentContacts.get(i).getLastName().trim().equalsIgnoreCase(lastName)) {
                currentContacts.get(i).printInfo();
                found = true;
            }
        }
        if (!found) {
            System.out.println("Sorry. Contact with last name: " + lastName + " not found.");
        }
    }

    /**
     * Saves the current list of contacts onto the disk
     * 
     * @author Arman
     */
    public void write() {
        FileOutputStream outFile;
        ObjectOutputStream outObject;
        try {
            outFile = new FileOutputStream("data");
            outObject = new ObjectOutputStream(outFile);
            outObject.writeObject(currentContacts);
            outObject.writeObject(currentContacts);
            outFile.close();
            outObject.close();
        } catch (IOException ioe) {
            System.out.println("Error writing objects to the file: " + ioe.getMessage());
        }
    }

    /**
     * Reads any saved data from the disk into memory, and stores it in the
     * currentContacts
     * 
     * @author Arman
     */
    public void read() {
        FileInputStream inFile;
        ObjectInputStream inObject;
        try {
            inFile = new FileInputStream("data");
            inObject = new ObjectInputStream(inFile);
            currentContacts = (ArrayList<Contact>) inObject.readObject();
            currentContacts = (ArrayList<Contact>) inObject.readObject();
            inFile.close();
            inObject.close();
        } catch (IOException ioe) {
            System.out.println("Error reading from the file: " + ioe.getMessage());
        } catch (ClassNotFoundException cnfe) {
            System.out.println(cnfe);
        }
    }

}

public class Contact implements Comparable <Contact> {

    private String firstName;
    private String lastName;
    private String streetAddress;
    private String emailAddress;
    private String phoneNumber;
    private String notes;

    /**
     * Set the last name for contact
     * 
     * @author Arman
     */
    public Contact(String lastName) {
        this.lastName = lastName;
    }
    /**
     * Return last name of the contact
     * @author Zhixiang
     */
    public String getLastName(){
        return lastName;
    }
    /**
     * Sets the last name of the contact
     * @author Nick
     */
    public void setLastName(String newLastName){
        this.lastName = newLastName;
    }
    /**
     * Prints out all data on the contact, formatted for user viewing.
     * @author Zhixiang
     */
    public void printInfo(){
        System.out.println("Name:    "+ getFirstName() + " " + getLastName());
        System.out.println("Phone:   "+ getPhoneNumber());
        System.out.println("Address: "+ getStreetAddress());
        System.out.println("Email:   "+ getEmailAddress());
        System.out.println("Notes:   "+ getNotes());
        System.out.println();
    }


    /**
     * Returns the contact's first name
     * 
     * @author Nick
     */
    public String getFirstName() {
        return firstName;
    }

    /**
     * Assigns the contact's first name
     * 
     * @author Nick
     */
    public void setFirstName(String newFirstName) {
        firstName = newFirstName;
    }

    /**
     * Returns the contact's street address
     * 
     * @author Nick
     */
    public String getStreetAddress() {
        return streetAddress;
    }

    /**
     * Assigns the contact's street address
     * 
     * @author Nick
     */
    public void setStreetAddress(String newStreetAddress) {
        streetAddress = newStreetAddress;
    }

    /**
     * Returns the contact's email address
     * 
     * @author Nick
     */
    public String getEmailAddress() {
        return emailAddress;
    }

    /**
     * Assigns the contact's email address
     * 
     * @author Nick
     */
    public void setEmailAddress(String newEmailAddress) {
        this.emailAddress = newEmailAddress;
    }

    /**
     * Returns the contact's phone number
     * 
     * @author Nick
     */
    public String getPhoneNumber() {
        return phoneNumber;
    }

    /**
     * Assigns the contact's phone number
     * 
     * @author Nick
     */
    public void setPhoneNumber(String newPhoneNumber) {
        this.phoneNumber = newPhoneNumber;
    }

    /**
     * Returns the contact's notes
     * 
     * @author Nick
     */
    public String getNotes() {
        return notes;
    }

    /**
     * Assigns the contact's notes
     * 
     * @author Nick
     */
    public void setNotes(String newNotes) {
        this.notes = newNotes;
    }

    /**
     * Return formatted entire contact information
     * @author Arman
     */
    public String toString(){
        return firstName + " " +  lastName + " " + streetAddress + " " + emailAddress + " " + phoneNumber + " " + notes ;
    }

    /**
     * Allow making comparison between contacts for sorting
     * Compares this contact to the contact you specify.  Compares by last name then first name alphabetically.
     * Returns -1 if this contact comes before the other, returns 0 if they are exactly the same name, returns 1 if this comes after the other one.
     * @author Nick
     */
    public int compareTo(Contact otherContact){
        if (this.lastName.toLowerCase().compareTo(otherContact.lastName.toLowerCase()) <= -1) {
            return -1;
        }
        else if (this.lastName.toLowerCase().compareTo(otherContact.lastName.toLowerCase()) >= 1){
            return 1;
        }
        else if (this.firstName.toLowerCase().compareTo(otherContact.firstName.toLowerCase()) <= -1){
            return -1;
        }
        else if (this.firstName.toLowerCase().compareTo(otherContact.firstName.toLowerCase()) >= 1){
            return 1;
        }
        else return 0;
    }

}

public class Contact implements Comparable<Contact>, Serializable {
    private static final long serialVersionUID = 1L;
}

public class ContactList {
    private static final long serialVersionUID = 1L;
}