How can I call abstract class methods from another class

[srinivas2828]

Hi experts I have a problem that I couldn't able to figureit so I thought to post in a forum so the problem is I have one abstract class(class only abstract) not any of methods in this calss are anstract ,then I want to call some of methods in my own class which extends from abstract class.But the thing is that I called the methods but its returning null for all methods which I am calling . So tell me whats wrong with this code.

MovingObject.java which is a abstract class and I have written one more class init which extends from abstract class

package traffic.object;
import java.io.*;
import java.util.*;
import traffic.*;
import rescuecore.OutputBuffer;
import rescuecore.RescueConstants;

public abstract class MovingObject extends RealObject implements Obstruction {
    public MovingObject(int id) {
        super(id);
    }

    private int m_position;
    private double m_positionExtra;
    // private int m_direction;
    // private int[] m_positionHistory;
    private Route m_routePlan;

    public void setRoutePlan(Route route) {
        m_routePlan = route;
    }

    public Route routePlan() {
	System.out.println("routeplan = " + m_routePlan);       
	return m_routePlan;
    }
}

class MyMovingObject extends MovingObject{
    public MyMovingObject(int id) {
	super(id);
    }

    public MyMovingObject() {
	this(0);
    }
    public int type() {
	rerurn 1;
    }

    public void Calculate() {
	MovingObject mv = new MyMovingObject();
	mv.routePlan();
	System.out.println(mv.routePlan());
    }
}

Now I am calling some methods from this class names Simulator.java

package traffic;
import java.net.*;
import java.util.*;
import traffic.object.*;


public class Simulator extends MyMovingObject implements Constants {
    private final IO io;
	private int id;

    public Simulator(InetAddress kernelAddress, int kernelPort) {
        io = new TCPIO(kernelAddress, kernelPort);
        io.sendConnect();
        id = io.receiveConnectOk();
        System.out.println("Connected. Simulator ID is " + id);
        io.sendAcknowledge();
     
    }



    public void simulate() {
        System.out.println("start");
        while (true) {
	    System.out.println(" receiving commands from kernel"); 
           io.receiveCommands();
            System.out.println("time: " + WORLD.time());
            move();
	    System.out.println("sending updates to kernel");
            io.sendUpdate();
	    System.out.println("receiving updates from kernel");
            io.receiveUpdate();
        }
    }
    
    public void move() {
	MyMovingObject mo = new MyMovingObject();
	mo.Calculate();
	System.out.println("working on that");
    }
}

experts please help me out this problem..when I am callingmethods its returning Null...
Thanks in Advance

[StormyWaters]

    public void Calculate() {
	MovingObject mv = new MyMovingObject();
	mv.routePlan();
	System.out.println(mv.routePlan());
    }

Why are you creating a new instance of MyMovingObject, just use the current one you are in. And where do you set the m_routePlan variable?

[srinivas2828]

well Thanks for your reply I did not set the variable because just calling that method will return the routeplan and it will print(I guess so) if I am set the variable it is giving erorrs

[StormyWaters]

I'm guessing its the routePlan() method is the method returning null right?

What method/s are returning null? Usually this is because something isn't set correctly.

[srinivas2828]

exactly Stormy Waters
the methods which I am calling from abstract class all re returning Null values...
this is what I am trying to figure it out..

[StormyWaters]

Is it possible that its returning null because the value is actually null?

As far as I can tell, you are never setting the m_routePlan variable anywhere, so it is indeed null. The method is getting called correctly.

[srinivas2828]

I called saperately from main program it returning list of objects but m_routePlan will initialize in the abstract class itself no(correct me fi I am wrong) ,In that abstract class we have two methods which one is use to set the routeplan and another one is to return the routeplan, btw I am calling only routePlan method from abstract class,Do I need to call setRoutePlan method before call to routePlan method?

[srinivas2828]

The thing is that I need to call setRoutePlan method before calling routePlan so I did it.but this time I am getting zero instead of Null ..

changes I made to the Code

 public void move() {
	MyMovingObject mo = new MyMovingObject();
	Route route = new Route(1);
       	mo.setRoutePlan(route);
	//	System.out.println(route);
	System.out.println(" this is the routeplan =" + mo.routePlan());
	System.out.println("working on that");

[Fubarable]

Why does Simulator extend MyMovingObject? Perhaps you need to show more code.

[srinivas2828]

Because I want to use methods in abstract class . Actually I want to call some methods in Abstract class and I have written one class which extends abstract class so sub-class will have all the methods which are in abstract class.And I have written one more class Simulator.java which extends from sub-class,and I am calling sub-class methods in this class only.
there are the codes

MovingObjec.java

public abstract class MovingObject extends RealObject implements Obstruction {
    public MovingObject(int id) {
        super(id);
    }

    private int m_position;
    private double m_positionExtra;
    private Route m_routePlan;

    public void setRoutePlan(Route route) {
	m_routePlan = route;
    }
// I want to call this method and I want to use this method returned value in Simulator.java
    public Route routePlan() {
	// System.out.println("then second this to get route plan");
// 	System.out.println("routeplan = " + m_routePlan);       
	return m_routePlan;
    }

I have written sub-class which extends from super class(MovingObjec.java) Now this class will contain all the methods which are in superclass
MyMovingObject.java

public class MyMovingObject extends MovingObject {
    public MyMovingObject(int id) {
	super(id);
    }
    
    public MyMovingObject() {
	this(0);
    }
    public int type() {
	return 1;
    }
    
}

Now I have written one more class which extends from MyMovingObject.java so I am calling some methods to perform tasks
Simulator.java

public class Simulator extends MyMovingObject implements Constants {
    private final IO io;
    private int id;
    

    public Simulator(InetAddress kernelAddress, int kernelPort) {
        io = new TCPIO(kernelAddress, kernelPort);
        io.sendConnect();
        id = io.receiveConnectOk();
        System.out.println("Connected. Simulator ID is " + id);
        io.sendAcknowledge();
	
    }
    
    
    
    public void simulate() {
        System.out.println("start");
        while (true) {
	    //System.out.println(" receiving commands from kernel"); 
	    io.receiveCommands();
            System.out.println("time: " + WORLD.time());
            move();
	    //System.out.println("sending updates to kernel");
            io.sendUpdate();
	    //    System.out.println("receiving updates from kernel");
            io.receiveUpdate();
        }
    }
    
    public void move() {
	MyMovingObject mo = new MyMovingObject();
	Route route = new Route(1);
       	mo.setRoutePlan(route);
	//	System.out.println(route);
	System.out.println(" this is the routeplan =" + mo.routePlan());
	System.out.println("working on that");
	
	
    }
}

[Fubarable]

Because I want to use methods in abstract class .

But is Simulator a MovingObject, or should it have MyMovingObject objects? I fear that you're mistaken on what inheritance is for as having Simulator subclass MyMovingObject may not be how you do this. Instead perhaps you should use a "has-a" relationship, not an "is-a" relationship.

[srinivas2828]

No,Simulator Have MyMovingObjects. I did a silly mistake which I am not able to figureit out for the couple of days..., I have one silly question before I aks,I should say sorry for this.fogive my poor java knowledge

First I am extending sub-clss from super class this is okay,but I am again extending one more class from sub-class,is this Right?

[Fubarable]

First I am extending sub-clss from super class this is okay,but I am again extending one more class from sub-class,is this Right?

In many situations, yes this is fine.

Does it apply to your situation? Myself, I don't have enough information to answer this.

Best of luck.

[srinivas2828]

okay thanks for your support