Question

please write code in java, assignment is due soon Thanks.

public interface Named

The Named interface is a simple interface which applies to anything which has a name. The only thing required is the following method:

• String name() which returns the name of the instance.

public interface MessageSink, It includes:

void deliver(Named sender, String message) delivers the specified message from the given sender.

public interface Sharable, which is Named, It includes no method.

public abstract class GeneralCapability It incudes:

• The getter and setter getOwner and setOwner, for the Named participant who owns the user interface.
• The getter getSharable, for the Sharable currently associated with the Capability.
• @Override public void linkSharable(Sharable s) creates an association between the input Sharable and this object, if the Sharable is a compatible type. If it is not a compatible type (which recognizeSharable will tell us), then it should throw a SharableException with the message "cannot handle Sharable NAME", where NAME is the name of the Sharable. Likewise, if the Capabilitiy has already been associated with a different Sharable, then it should throw a SharableException with the message "Capability is already linked to a Sharable". Otherwise, we would create the association with the Sharable. What do we mean when we say create an association? Maybe it would help to think of this as an ordinary setter method with a few extra checks built-into it.
• @Override public void unlinkSharable(Sharable s) will disassociate the current Sharable from the object (sets it to null); unless the input is either null or some completely different Sharable, in which case it would throw a SharableException with the message "non-matching Sharable".

public class Chat, which is Sharable, It includes following method

• public void send(Named sender, String message) delivers the specified message to all of the MessageSinks in the list, in order.
• public void addSink(MessageSink s) adds a MessageSink to the list of sinks.
• public boolean removeSink(MessageSink s) removes the specified MessageSink from the list of sinks, returning true if the sink was found and removed, and false otherwise.
• @Override public String name() returns the string "chat".

public class ChatHandler, which is a GeneralCapability and provides MessageSink

It must have the following methods:

• public Chat getChat() returns the Chat object associated with this capability, or null if there isn't an association yet.
• @Override public boolean recognizeSharable(Sharable s) returns true only if the Sharable is a Chat.
• @Override public void linkSharable(Sharable s) in addition to linking the Sharable as in the GeneralCapability class, this method should register the ChatHandler as a MessageSink for the Chat feed by using its addSink method.
• @Override public void unlinkSharable(Sharable s) in addition to unlinking the Sharable as in the GeneralCapability class, this method should deregister the ChatHandler as a MessageSink from the Chat feed by using its removeSink method.
• public void send(String message) if the Chat is associated, then this method will send the specified message to the Chat feed from the current user.
• @Override public void deliver(Named sender, String message) will print out the incoming message in the format "USER: MESSAGE" (including a newline).

Answer 1

ANSWER :

Java codes to copy:-

package interface_problem;

public interface Named {
//Returns the name of the instance(in the implemented class)
String name();
}

package interface_problem;

public interface Sharable extends Named{

}

package interface_problem;

public interface MessageSink {
//Delivers the specified message from the given sender
void deliver(Named sender, String message);
}

package interface_problem;

public abstract class GeneralCapability {
//Named participant who owns the user interface
private Named owner;
//Sharable currently associated with the Capability
private Sharable sharable;
  
  
public Named getOwner() {
return owner;
}
  
public void setOwner(Named owner) {
this.owner = owner;
}
  
public Sharable getSharable() {
return sharable;
}
  
//Creates an association between the input Sharable and this object,following constraints
public void linkSharable(Sharable s) throws SharableException
{
//Checking if the Sharable is a compatible type
if (this.recognizeSharable(s))
this.sharable = s;
//Checking if the Capabilitiy has already been associated with a different Sharable
else if(this.sharable != null)
throw new SharableException("Capability is already linked to a Sharable");
//If it is not a compatible type
else
throw new SharableException("cannot handle Sharable " + s.name());
  
}
//To disassociate the current Sharable from the object
public void unlinkSharable(Sharable s) throws SharableException
{
if(s != null && (s instanceof Chat))
this.sharable = null;
//If the input is either null or some completely different Sharable
else
throw new SharableException("non-matching Sharable");
  
}
//Implementation in child class
public abstract boolean recognizeSharable(Sharable s);
  
  

}

package interface_problem;

public class ChatHandler extends GeneralCapability implements MessageSink{
  
//Chat object which is null
private Chat obj;
//Returns chat object associated with this capability, or null if there isn't an association yet.
public Chat getChat()
{
return obj;
}
  
public void linkSharable(Sharable s) throws SharableException
{
super.linkSharable(s);
//Registers the ChatHandler as a MessageSink for the Chat feed.
((Chat)getSharable()).addSink(this);
}
  
public void unlinkSharable(Sharable s) throws SharableException
{
super.unlinkSharable(s);
//Deregister the ChatHandler as a MessageSink from the Chat feed
obj.removeSink(this);
}
  
//Checks if the Sharable is a Chat
public boolean recognizeSharable(Sharable s)
{
return s instanceof Chat;
}
  
public void send(String message)
{
//If the Chat is associated
if(getSharable() != null)
//send the specified message to the Chat feed from the current user.
((Chat)getSharable()).send(getOwner(), message);
}
//Print out the incoming message in the format "USER: MESSAGE" (including a newline)
public void deliver(Named sender, String message)
{
System.out.println(sender.name() + ":" + message + "\n");
}
}

package interface_problem;

import java.util.ArrayList;
import java.util.List;

public class Chat implements Sharable{
  
//List of sink
private List<MessageSink> sink_list = new ArrayList<>();
  
//Delivers the specified message to all of the MessageSinks in the list, in order(as list
//maintains insertion order
public void send(Named sender, String message)
{
for(MessageSink each:sink_list)
{
each.deliver(sender, message);
}
}
//Adds a MessageSink to the list of sinks
public void addSink(MessageSink s)
{
sink_list.add(s);
}
  
// Removes the specified MessageSink from the list of sinks,
//returning true if the sink was found and removed, and false otherwise.
public boolean removeSink(MessageSink s) {
return sink_list.remove(s);
}
//Returns the string "chat".
@Override
public String name() {
return "chat";
}
  
}

package interface_problem;

public class SharableException extends Exception {
  
public SharableException(String message)
{
super(message);
}
}

package interface_problem;

public class Demo {

public static void main(String[] args) {
  
//Creating chat and chathandler instances
Chat chat = new Chat();
  
ChatHandler handler = new ChatHandler();
  
//Linking the chat with the handler
try {
handler.linkSharable(chat);
} catch (SharableException e) {
System.out.println(e.getMessage());
  
}
//Setting the owner of the sharable
handler.setOwner(chat);
  
handler.send("Hello");
  
//Handling exceptions by deliberately setting chat instance to null
chat = null;
  
try {
handler.unlinkSharable(chat);
handler.linkSharable(chat);
} catch (SharableException e) {
  
System.out.println(e.getMessage());
}
  
  
}

}

Screenshot of a sample output:-

chat:Hello non-matching Sharable Picked up _JAVA_OPTIONS: -Xmx512M