well...nothing is purely oop or procedural. But some have more support for oop concepts and doing oop stuff. Java has many classes that supports oop porgramming methods which makes the programmer's life eay. So many say it is an oop language. You can write programs in procedural way in Java too if you want.
One of the main difference betwen oop and procedural programming is that in OOP, you can create OBJECTS and work with them easiliy which makes your life easier. in procedural programming, there are no so called Objects. So it is like you have to repeat most of the things again and again. Well...this is not a big explnation. You should know whatis an object to understand this.
this book called "head first java" answers your question with examples very nicely in their first pages. You should read it. At least first few pages to get a real answer.
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...