Run Method on elements in a Vector

[Jezternz]

Ok, basicly I have created a Class.

public class ClassX{
	public ShapeObj(){}
	public doThis(){}
}

And I have created a Vector and filled it with instances of this new class.

Vector xv = new Vector();
xv.add(new ClassX());
xv.add(new ClassX());
xv.add(new ClassX());
xv.add(new ClassX());

Now I want to traverse through the Vector (preferably efficiently) and run the method (doThis) on each element. This is what I have:

ListIterator it = objlist.listIterator();
while(it.hasNext()){
	[B][U][I]ClassX temp = it.next();[/I][/U][/B]
	temp. doThis();
}

The problem is, the compiler is complaining that it can only return an 'object' from the iterator. So naturally I tried changing it to this:

ListIterator it = objlist.listIterator();
while(it.hasNext()){
	Object temp = it.next();
	[B][U][I]temp. doThis();[/I][/U][/B]
}

This was wishfull thinking though, as now the next line is the problem, as obviously the Object Class doesnt have a doThis() Method.
So how can I cycle through the vector and run a method on each element?

Cheers, Josh

[JosAH]

Use generics: you don't just have a raw Vector but a Vector<ClassX> that contains only classX objects. It gives you a dedicated iterator: Iterator<ClassX > that returns a ClassX object each time you ask for it.

kind regards,

Jos

[Jezternz]

What do you mean by generics?
Anyway I managed to get in contact with an old tutor, and he told me all I had to change was below:

ListIterator it = objlist.listIterator();
while(it.hasNext()){
    ClassX temp = [B][I][U](ClassX)[/U][/I][/B]it.next();
    temp. doThis();
}

[JosAH]

What do you mean by generics?
Anyway I managed to get in contact with an old tutor, and he told me all I had to change was below:

ListIterator it = objlist.listIterator();
while(it.hasNext()){
    ClassX temp = [B][I][U](ClassX)[/U][/I][/B]it.next();
    temp. doThis();
}

Yes, that's the old fashioned way of doing it: cast the Object to the type you want. Generics do the same but they do it compile safe. Read the tutorials; it was introduced in Java 1.5 and you should use it.

kind regards,

Jos

[Jezternz]

Thanks heaps, here are the two lines that need to be changed for generics use.

Vector<ClassX> xv = new Vector();

and

ListIterator<ClassX> it = objlist.listIterator();
while(it.hasNext()){
    ClassX temp = it.next();
    temp. doThis();
}

[JosAH]

Thanks heaps, here are the two lines that need to be changed for generics use.

Vector<ClassX> xv = new Vector();

and

ListIterator<ClassX> it = objlist.listIterator();
while(it.hasNext()){
    ClassX temp = it.next();
    temp. doThis();
}

Almost, make that:

Vector<ClassX> xv = new Vector<ClassX>();

It tells the compiler that xv is a reference to a vector of ClassX elements. But yes, generics are better than explicit casts all over your code. Generics are a compile time issue, i.e. during runtime those types are checked by the compiler and erased.(i.e. they have become ordinary Object types again).

kind regards,

Jos