This should work. You need to declare the variable cchild to be a static member of the JavaApplicaiton1 class to be able to access it statically. 

 class sample
 {
 public static int x;
 public int y;
 sample()
 {
 x=0;
 }
 }

 public class JavaApplication1 {

 // NEW BIT - by making this variable static we can now access it without needing an instance of the object.
 static sample cchild=new sample();

 public static void main(String[] args) {
 sample.x=0;
 cchild.x=9;
 }
 }

There a re a few other things you might do differently in this code example. The first is that I would suggest that you use the Java naming convention of starting the name of your classes with a capital letter (Sample instead of sample in this case) otherwise they do not look like class names to Java people.