How many types of AWT layouts are there in Java?

Which version of Java introduced annotations?

The order of enum variables is

What is a Collection in Java?

How to set a classpath

Which of the following is used to make a thread wait until the completion of previous thread.

What is a vector in Java?

How can a constructor be used for a servlet?

What is a Callable in Java?

Predict the output of the following Java code:

class Abekus {
public static void main(String args[])
{
String s1 = "Welcome to ";
String s2 = "Abekus";
System.out.println(s1.concat(s2));
}
}