Thread: How to create a pointer type of effect for objects

Hi I have a class with two methods referring a session object. I want to modify it and make it work to handle two sessions running parallely. So based if a new session comes within a session I want to assign the new session to another variable. You know I don't want to modify the class severely. I just want to use a boolean variable that checks the status and assign the session to one of the two variables and the res of the logic will run smoothly. Here is the frameowrk of my class

Public class MyClass
{
        private IoSession clientSession = null; 
	private IoSession serverSession = null;
        private IoSession newServerSession = null;
 
public void passToServer( RtspMessage message )
	{
//I include the following assignment statment and if statement to make is work for two sessions
 
               /* IoSession serverSession =null;
                 if (this.sessionWithinASession==true)
                {
                    serverSession=this.newServerSession; //This is my question
                }
                else
                {
                    serverSession=this.serverSession; //This is my question. I want the variable serverSession (the local one to point to the two global variables). So, tell me if I'm wrong and how I can implement.
 
...
 
if ( serverSession == null ) {
				RtspRequest request = (RtspRequest) message;
				try {
					connectServerSide( request.getUrl() );
 
				} catch ( IOException e ) {
					log.error( e );
					// closeAll();
				} finally {
					if ( serverSession == null )
						return;  //I know connectServerSide Creates a new serversession and assigned it to the external one but it terminates b/c this is not referring the global one
				}
			}
}
 
private void connectServerSide( URL url ) throws IOException
	{
            //This is to also another code that i included for the same reason that I mentioned above
                IoSession serverSession =null;
                if (this.sessionWithinASession)
                    serverSession=this.newServerSession;
                else
                    serverSession=this.serverSession;
 
......
	// Create TCP/IP connector.
		SocketConnector connector = new SocketConnector(); 
		// Start communication.
		log.debug( "Trying to connect to '" + host + "' " + port + " URL is "+url);
		try {
 
		ConnectFuture future = connector.connect(
					new InetSocketAddress( host, port ), new ServerSide(),
					new RtspServerFilters() );
			future.join();
			serverSession = future.getSession(); //I suppose this will modify the local and also the global and was thinking that by the time it gets back to the previous method serverSession will not be null
 
		} catch ( UnresolvedAddressException e ) {
 
		    return;
		}
 
}

So as you see the connect server side creates a session and should assign to the proper global variable. But in PassToServer method after the control gets back serverSession (which I think is refering to either the global serversession and global newserversession is still null). I hope my question is clear. Basically my question is how can I point an object from a method using the same type of object and modify the pointer and get the effect on the global object.

Thank you




}

Ok, well I say this a lot. There is no good reason to have local variables and global variables have the same name. That sort of thing just creates the kind of confusion you are having here. With that said, your attempt to set the global variable to be equal to the local variable is flipped. This:

serverSession=this.serverSession;

should be:

this.serverSession=serverSession;

The keyword this is used to reference the class you are in, not the method you are in. Based on basic programming, the variable you are setting is on the left of the equals sign and the value you are assigning said variable is on the right of the equals sign. Which means, your call to this.serverSession needs to be on the left, as you are attempting to assign that value.

My best advice to you is to not have local and global variables with the same name, this can cause some confusion in your programs and serves no benefit. What changing the local variable name would look like is:
Instead of this:

Public class MyClass
{
        private IoSession clientSession = null;
    private IoSession serverSession = null;
        private IoSession newServerSession = null;
 
public void passToServer( RtspMessage message )
    {
//I include the following assignment statment and if statement to make is work for two sessions
 
               /* IoSession serverSession =null;
                 if (this.sessionWithinASession==true)
                {
                    this.serverSession=newServerSession; //This is my question
                }
                else
                {
                    this.serverSession=serverSession; //This is my question. I want the variable serverSession (the local one to point to the two global variables). So, tell me if I'm wrong and how I can implement.
 
...

You would have this:

public class MyClass
{
        private IoSession clientSession = null;
    private IoSession serverSession = null;
        private IoSession newServerSession = null;
 
public void passToServer( RtspMessage message )
    {
//I include the following assignment statment and if statement to make is work for two sessions
 
                IoSession serverSession2 =null;
                 if (sessionWithinASession==true)
                {
                    serverSession=newServerSession; //This is my question
                }
                else
                {
                    serverSession=serverSession2; //This is my question. I want the variable serverSession (the local one to point to the two global variables). So, tell me if I'm wrong and how I can implement.
 
...

Going from that, I have more questions:
1) Where is the variable sessionWithinASession?
2) If it is a boolean, why bother compare to true? If you are checking if boolean sessionWithinASession is true, you only need to say: if (sessionWithinASession) as sessionWithinASession will return a true or false value, which is what an if statement looks for.
3) Inside the if statement I mentioned above, are you attempting to set the global variable serverSession or the local variable serverSession?
4) Why do you have 3 IoSessions? What is the purpose of having 3 instead of 2? 1 for the client and 1 for the server.

Originally Posted by Darryl.Burke

The OP is apparently conditionally setting the local variable equal to one of two instance fields.
And in Java, the nearest thing to a global variable is a static (and usually final) class field, or an interface field. An instance field is, well, an instance field, but may equally well be referred to just as a field.
db

Thanks. This is a good information. By the way as I said earlier, I want to modify the local variable hoping to affect the global (as a side effect).