Java

class SerialObject extends ObjectType{ 
     int serialPortNo; 
} 
 
class IPObject extends ObjectType{ 
     String host=""; 
     int port; 
}

Exception in thread "main" java.lang.NullPointerException<br />
at DiffObjectClasses.main(DiffObjectClasses.java:9)

interface IPrintable
{
     void Print();
}

class SerialObject implements IPrintable{ 
     int serialPortNo;
     public SerialObject(int portno)
     {
          serialPortNo = portno;
     }
     public void Print()
     {
          System.out.println("Serial port no:" + serialPortNo);
     }
} 
 
class IPObject implements IPrintable{ 
     String host; 
     int port;
     public IPObject(String host, int port)
     {
          this.host = host;
          this.port = port;
     }
     public void Print()
     {
          System.out.println("IP host:" + host); 
          System.out.println("IP port:" + port);
     }
}

class DiffObjectClasses{
	public static void main(String [] args)
	{
		SerialObject so;
		IPObject iob;
		
		ObjectType ot[] = new ObjectType[3];
		
		ot[0]=new ObjectType();	// This was added!!!	
		ot[0].objectID=1;
		ot[0].objectType=1;
		so=new SerialObject();
		so.serialPortNo=21;
		ot[0].objectContent=so;
		
		ot[1]=new ObjectType();	// This was added!!!
		ot[1].objectID=2;
		ot[1].objectType=1;
		so=new SerialObject();
		so.serialPortNo=21;
		ot[1].objectContent=so;
		
		ot[2]=new ObjectType();	// This was added!!!
		ot[2].objectID=3;
		ot[2].objectType=2;
		iob=new IPObject();
		iob.host="localhost";
		iob.port=2200;
		ot[2].objectContent=iob;
		
		System.out.println("----------------------------");
		for(int indx=0; indx<ot.length;indx++)
		{
			System.out.println("ObjID:"+ot[indx].objectID);
			System.out.println("ObjType:"+ot[indx].objectType);
			switch(ot[indx].objectType)
			{
				case 1:
						so=(SerialObject)ot[indx].objectContent;
						System.out.println("Serial port no:"+so.serialPortNo);
						break;
				case 2:
						iob=(IPObject)ot[indx].objectContent;
						System.out.println("IP host:"+iob.host);
						System.out.println("IP port:"+iob.port);
						break;		
			}
		}
	}
}

class ObjectType extends Object{
	int objectID;
	int objectType;
	Object objectContent;
}

class SerialObject extends Object{
	int serialPortNo;
}

class IPObject extends Object{
	String host="";
	int port;
}

ana_ochia wrote:

we have this project at school