Just was typing a LinkedList code from 'Programming With Java'

[Vishal Hegde]

import java.util.*;
public class MyStack
{
  private LinkedList list=new LinkedList();
  public void push1(Object o)
   {
      list.addFirst(o);
   }
 public void push2(Object obj)
  {
    list.addLast(obj);
  }
public Object bottom()
  {
     return list.getLast();
  }
public Object pop()
  { 
   return list.removeFirst();
  }

public static void main(String args[])
 {
   Car myCar;
   Bird myBird;

 MyStack s=new MyStack();
s.push1(new Car());
s.push2(new Bird());
myCar=(Car)s.pop();
System.out.println("The first element in the List: "+myCar);
myBird=(Bird)s.bottom();
System.out.println("The last element in the List: "+myBird);
  
 }
}

class Car
{
  String car1,car2,car3,car4;
  Car()
  {
     car1="Benz";
     car2="Toyoto";
     car3="Qualis";
     car4="Santro";
  }
}
class Bird
{
  String bird1,bird2,bird3;
  Bird()
  {
   bird1="parrot";
   bird2="duck";
   bird3="raven";
  }
}

Output I got:
The first element in the List: Car@addbf1
The last element in the List: Bird@42e816


Output in Book:
The first element in the List: Benz
The last element in the List: raven

[Pavan Kumar Dittakavi]

I think, System.out.println ultimately calls the toString() method to display the contents. And since your code does not have the toString() method overridden, the one from the Object class gets picked up. That one, has the below implementation:

  public String toString() {
	return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }

and hence the result. Perhaps you should override it?

Thanks,
Pavan.

[Wendy Gibbons]

is this really all the code from the example?
as the car and bird class do nothing but create a load of strings. There is no way the code you have pasted can produce the output expected.

is it an exercise to make it work?

[Vishal Hegde]

Wendy Gibbons wrote:is this really all the code from the example?
as the car and bird class do nothing but create a load of strings. There is no way the code you have pasted can produce the output expected.

is it an exercise to make it work?

Yes its on page 350 Books name is Programming with Java(A Primer 3e) by E.BalaguruSamy

[Jeff Verdegan]

Vishal Hegde wrote:

Wendy Gibbons wrote:is this really all the code from the example?
as the car and bird class do nothing but create a load of strings. There is no way the code you have pasted can produce the output expected.

is it an exercise to make it work?

Yes its on page 350 Books name is Programming with Java(A Primer 3e) by E.BalaguruSamy

Well, if it is an exercise to make it work then I would expect that just typing it in does not give the desired output. The whole point in that case is that you are supposed to figure out what's missing. Presumably the topics covered in that section will give you a big hint.

If, on the other hand, that's not the case, that is, if you're supposed to be able to just type it and run it an get the same results, then either the book has an error or you made a mistake.

[Winston Gutkowski]

Pavan Kumar Dittakavi wrote:I think, System.out.println ultimately calls the toString() method...

<Friday pedant>
You're not quite right. It actually uses String.valueOf(Object) (as do most 'print' methods), which will, indeed, call the object's toString() method as long as it is not null.
</Friday pedant>

Winston