TreeMap class and message not understood issues - help please

Question

Can anyone help with this one please?
The code is the start of a Map interface/TreeMap class to hold names as keys and addresses as values (both Strings).
I think the instance variable and the constructor are correct, but the addAddress method throws an error
Semantic error: Message addAddress( java.lang.String, java.lang.String ) not understood by class'java.util.TreeMap'.
I can only guess that I've overlooked something quite simple? The line at the end of the code should read
"Replaced "old address" with "new address" for "new name" and this should only display if the key already exists in the Map,
hence the if statement. The keys and values have been declared as Objects for future flexibility. Sorry if this is all blatantly obvious.
Also if I wanted to test this code and create an instance of the Addressbook class, what should my code look like?
Many thanks.
{code}import java.util.*;
public class Addressbook
private static Map<Object, Object> addresses;
public Addressbook()
super();
this.addresses = new TreeMap<Object, Object>();
public static void addAddress(String name, String address)
if (addresses.containsKey(name))
addresses.put(name, address);
System.out.println("Replacing " + addresses.remove(name) + " with "
+ addresses.get(name) + " for " + name);
else
addresses.put(name, address);
{code}

Answer 1

If you're only going to store Strings in the Map, make sure you are specifying them as generics so that all operations return Strings by default.
You don't need to use contains if you are going to replace a map value. The old value will be returned when you place the new one in. Should be quicker, since you're not searching for the same key twice.
Do not refer to a static variable with this. it become confusing and could result in bugs. That said use static sparingly.
The AddressBook should probably be an instance and all the variables and methods should be instance variable and methods.
I don't know your requirements however so I'll leave this as a suggestion.
import java.util.*;
public class AddressBook {
   private static Map<String, String> addresses = new TreeMap<String, String>();
   public static void addAddress(String name, String address) {
      String oldAddress = addresses.put(name, address);
      if(oldAddress != null) {
            System.out.printf("Replacing %s with %s for %s%n", oldAddress, address, name);
    public static void main(String[] args) {
        addAddress("me", "123");
        addAddress("me", "321");
}Brushfire,