Yahoo use utf-8 when manipulate message bytes.

src/net/java/sip/communicator/impl/protocol/yahoo/AdHocChatRoomYahooImpl.java

@@ -162,7 +162,7 @@ public void removeParticipantPresenceListener(
     public Message createMessage(byte[] content, String contentType,
                                 String contentEncoding, String subject)
     {
-        return new MessageYahooImpl(new String(content), contentType,
+        return new MessageYahooImpl(new String(content, "UTF-8"), contentType,
             contentEncoding, subject);
     }
 

src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetAdHocMultiUserChatYahooImpl.java

@@ -482,7 +482,7 @@ public void fireLocalUserPresenceEvent(AdHocChatRoom chatRoom,
     public Message createMessage(byte[] content, String contentType,
         String contentEncoding, String subject)
     {
-        return new MessageYahooImpl(new String(content), contentType,
+        return new MessageYahooImpl(new String(content, "UTF-8"), contentType,
             contentEncoding, subject);
     }
 
@@ -661,7 +661,7 @@ public void conferenceMessageReceived(SessionConferenceEvent ev)
 
                 Message newMessage =
                     createMessage(
-                        formattedMessage.getBytes(),
+                        formattedMessage.getBytes("UTF-8"),
                         OperationSetBasicInstantMessaging.HTML_MIME_TYPE,
                         OperationSetBasicInstantMessaging.DEFAULT_MIME_ENCODING,
                         null);

src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetBasicInstantMessagingYahooImpl.java

@@ -152,7 +152,7 @@ public void sendInstantMessage(Contact to, Message message)
                 return;
             
             byte[] msgBytesToBeSent = msgDeliveryPendingEvt.getSourceMessage().
-                getContent().trim().getBytes();
+                getContent().trim().getBytes("UTF-8");
 
             // split the message in parts with max allowed length
             // and send them all
@@ -173,13 +173,13 @@ public void sendInstantMessage(Contact to, Message message)
                     
                     yahooProvider.getYahooSession().sendMessage(
                         toUserID,
-                        new String(tmp1));
+                        new String(tmp1, "UTF-8"));
                 }
                 else
                 {
                     yahooProvider.getYahooSession().sendMessage(
                         toUserID,
-                        new String(msgBytesToBeSent));
+                        new String(msgBytesToBeSent, "UTF-8"));
                 }
                 
                 MessageDeliveredEvent msgDeliveredEvt