如何使收件人的名称对邮件系统不区分大小写？

Question

I have the following classes in the project:

• MailServer
• MailClient
• MailItem

I have to modify the MailServer so that it uses a HashMap to store MailItems instead of an ArrayList. The keys to the HashMap must be the names of the recipients, and each value must be an ArrayList containing all the MailItems stored for that recipient.The names of the recipients must be case-insensitive, ie “paul” and “Paul” and “PAUL” are all the same person.

I'm not sure how or where to start for setting up the mail system where the names of the recipients are case insensitive. Would appreciate any help. Thanks.

Below is my source code:

      import java.util.ArrayList;
        import java.util.List;
        import java.util.Iterator;
        import java.util.HashMap;

        /**
 * A simple model of a mail server. The server is able to receive
 * mail items for storage, and deliver them to clients on demand.
 * 
 * @author David J. Barnes and Michael Kölling
 * @version 2011.07.31
 */
public class MailServer
{
    // Storage for the arbitrary number of mail items to be stored
    // on the server.
    private HashMap<String, ArrayList<MailItem>> items;
    /**
     * Construct a mail server.
     */
    public MailServer()
    {
        items = new HashMap<String, ArrayList<MailItem>>();

    }

    /**
     * Return how many mail items are waiting for a user.
     * @param who The user to check for.
     * @return How many items are waiting.
     */
    public int howManyMailItems(String who)
    {
        int count = 0;
        for(String name : items.keySet()) {
            if(who != null) {
                who = formatName(who);
            }
            if(items.containsKey(who)) {
                count ++;
            }
        }
        return count;
    }

    /**
     * Return the next mail item for a user or null if there
     * are none.
     * @param who The user requesting their next item.
     * @return The user's next item.
     */
    public MailItem getNextMailItem(String who)
    {
        if(who != null) {
            who = formatName(who);
        }
        ArrayList<MailItem> mails = items.get((who));
        if(mails == null) {
            return null;
        }
        Iterator<MailItem> it = mails.iterator();
        while(it.hasNext()) {
            MailItem mail = it.next();
            if(mail.getTo().equals(who)) {
                it.remove();
                return mail;
            }
        }
        return null;

    }

    /**
     * Add the given mail item to the message list.
     * @param item The mail item to be stored on the server.
     */
    public void post(MailItem item)
    {
        String who = item.getTo();
        if(who != null) {
            who = formatName(who);
        }
        if(!items.containsKey(who)) {
            items.put(who, new ArrayList<MailItem>());
        }
        items.get(who).add(item);
    }

    private static String formatName(String who) {
        if(who.length() > 0) {
            return who.toLowerCase();
        }
        return "";
    }
}
/**
 * A class to model a simple email client. The client is run by a
 * particular user, and sends and retrieves mail via a particular server.
 * 
 * @author David J. Barnes and Michael Kölling
 * @version 2011.07.31
 */
public class MailClient
{
    // The server used for sending and receiving.
    private MailServer server;
    // The user running this client.
    private String user;

    /**
     * Create a mail client run by user and attached to the given server.
     */
    public MailClient(MailServer server, String user)
    {
        this.server = server;
        this.user = user;
    }

    /**
     * Return the next mail item (if any) for this user.
     */
    public MailItem getNextMailItem()
    {             
        return server.getNextMailItem(user);
    }

    /**
     * Print the next mail item (if any) for this user to the text 
     * terminal.
     */
    public void printNextMailItem()
    {
        MailItem item = server.getNextMailItem(user);
        if(item == null) {
            System.out.println("No new mail.");
        }
        else {
            item.print();
        }
    }

    /**
     * Send the given message to the given recipient via
     * the attached mail server.
     * @param to The intended recipient.
     * @param message The text of the message to be sent.
     */
    public void sendMailItem(String to, String subject, String message)
    {
        MailItem item = new MailItem(user, to, subject, message);
        server.post(item);  
    }
}

Answer 1

If I understand your question properly, recipients must be case-insensitive, and they are to be used as keys in a HashMap .

Why not just use the toLowerCase function on String, and use that version of the recipient as the key? That way, "PAUL", "Paul", and "paul" all get turned into "paul" for purposes of lookup.

You'd apply this by lowercasing the name input at the beginning of any function that uses it.

Answer 2

I would just convert all email-addresses to lower case:

String getEmailAddress(String emailAddress) {
    if (emailAddress.length() > 0) return emailAddress.toLowerCase();
    return ""
}

Hope this helps.