ArrayList 的对象排序使用可比较的

Question

所以我正在处理地址簿作业，我一直坚持使用 Comparable 来按姓氏对联系人进行排序。我正在尝试我们还没有真正学习过的东西，比如对象的 ArrayLists、可比较的和可序列化的，可比较的是最让我困惑的。

关于为什么联系人没有排序的任何提示？第二个问题，我想尝试将名字和姓氏的第一个字符设为大写，但我无法弄清楚所以我在 toString 方法中将整个字符设为大写，关于如何只获取第一个字符的任何想法上？

public class AddressBook implements Serializable{

private ArrayList<String> newBook = new ArrayList<String>();
private String dataFile;
private ArrayList<Contact> card =new ArrayList<Contact>(50);
private Contact[] contacts;
private int size = 0;
private int capacity = 0;
private String firstName;
private String lastName;


public static void main(String[] args) {
    AddressBook AB = new AddressBook();
    AB.addressBookMenu();
}


public void addressBookMenu() {
    Scanner scan = new Scanner(System.in);
    String option = "";

    System.out.println("PLEASE SELECT ONE OF THE FOLLOWING OPTIONS: ");
    System.out.println("\t add   --> Add a new contact ");
    System.out.println("\t find  --> Find a contact ");
    System.out.println("\t edit  --> Edit an existing contact ");
    System.out.println("\t view  --> View the current address book");
    System.out.println("\t save  --> Save the current address book");
    System.out.println("\t quit  --> quit");
    System.out.println();
    option = scan.nextLine();

    while(!(option.equalsIgnoreCase("quit"))) {
        Contact con = new Contact(firstName, lastName);
        if(option.equalsIgnoreCase("add")) {
            System.out.println("Enter First Name: ");
            String tempFirst = scan.nextLine();
            System.out.println("Enter Last Name: ");
            String tempLast = scan.nextLine();

            con.setFirstName(tempFirst);
            con.setLastName(tempLast); 
            card.add(con);  
            writeContact();
        }   

        //View address book
        if(option.equalsIgnoreCase("view")) {
            System.out.println("\tADDRESS BOOK" + "\n" +
                    "=============================");

            Collections.sort(card);
            con.getFullName();
            readContact();
        }

        System.out.println();
        System.out.println("PLEASE SELECT ONE OF THE FOLLOWING OPTIONS: ");
        System.out.println("\t add   --> Add a new contact ");
        System.out.println("\t find  --> Find a contact ");
        System.out.println("\t edit  --> Edit an existing contact ");
        System.out.println("\t view  --> View the current address book");
        System.out.println("\t save  --> Save the current address book");
        System.out.println("\t quit  --> quit");
        System.out.println();
        option = scan.nextLine();
    }
}

public void writeContact() {
    try (FileOutputStream out = new FileOutputStream("addressbook.txt")) {  
        ObjectOutputStream os = new ObjectOutputStream(out);

        os.writeObject(card);
        os.close();

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public void readContact() {
    try (FileInputStream in = new FileInputStream("addressbook.txt")) {
        ObjectInputStream is = new ObjectInputStream(in);
        ArrayList<Contact> card = (ArrayList<Contact>)is.readObject();

        for(Contact temp : card) {
            System.out.println(temp);
        }

        is.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
}

联系Class

public class Contact implements Comparable<Contact>, Serializable{

private String firstName;
private String lastName;
private String email;
private String phone;

public Contact() {
    firstName = "";
    lastName = "";
}
public Contact(String ln, String fn) {
    lastName = ln;
    firstName = fn;
}

public void setFirstName(String fn) {
    firstName = fn;
}
public void setLastName(String ln) {
    lastName = ln;
}
public void setFullName(String fn, String ln) {
    firstName = fn;
    lastName = ln;

}

public String getFirstName() {
    return firstName;
}
public String getLastName() {
    return lastName;
}
public String getFullName() {
    return lastName + firstName;
}

public String toString() {
    return 
            "FIRST NAME: " + getFirstName().substring(0).toUpperCase() + "\t" +
            "LAST NAME: " + getLastName().substring(0).toUpperCase() + "\n";            
}

@Override
public int compareTo(Contact nextContact) {
    return lastName.compareTo(nextContact.lastName);
}

}

Answer 1

Any tips on why the contacts aren't sorting?

他们正在整理。但是你不会打印排序的 card。您重新阅读 readContact 中的联系人，然后打印它们，未排序。

可能你打算这样写：

if(option.equalsIgnoreCase("view")) {
    System.out.println("\tADDRESS BOOK" + "\n" +
            "=============================");

    readContact();
    Collections.sort(card);
    printContacts();
}

并在 readContact 中更改此行：

    ArrayList<Contact> card = (ArrayList<Contact>)is.readObject();

为此：

    card = (ArrayList<Contact>)is.readObject();

并将打印从 readContact 移到它自己的方法中：

void printContacts() {
    for(Contact temp : card) {
        System.out.println(temp);
    }
}

Second question, [...] any ideas how to get only the first char upper?

当然可以，使用这样的辅助方法：

private String toTitleCase(String name) {
    return Character.toTitleCase(name.charAt(0)) + name.substring(1).toLowerCase();
}

Answer 2

您的问题如下：此代码片段

Collections.sort(card);
con.getFullName();
readContact();

实际上是对你拥有的 card 集合进行排序，然后你调用 readContact() 方法在其中创建一个本地 card 集合，它隐藏了 card 集合你有在你的主程序中，并打印它的联系人，因为它们之前被写入文件。他们没有得到排序。

解决方案是这样的：

if(option.equalsIgnoreCase("view")) {
    System.out.println("\tADDRESS BOOK" + "\n" +
                "=============================");

    con.getFullName(); // <------ ALSO, NOT QUITE SURE WHAT THIS IS FOR
    readContact();
}

public void readContact() {
    try (FileInputStream in = new FileInputStream("addressbook.txt")) {
        ObjectInputStream is = new ObjectInputStream(in);
        ArrayList<Contact> card = (ArrayList<Contact>)is.readObject();

        Collections.sort(card); // <----------- THIS ADDED

        for(Contact temp : card) {
            System.out.println(temp);
        }

        is.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

ArrayList 的对象排序使用可比较的

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comparable