How do I use multiple classes to print out different results

Question

I tried the below, but it only printed the print line from the class that contains the "main" method, but I want the second one (Demo2) to print to check some logic :
class StaticDemo {
int x;
static int y;
class Demo {
public static void main(String args[]){
StaticDemo.y = 30;
System.out.println("StaticDemo.y = " + StaticDemo.y);
class Demo2 {
public static void main(String args[]){
System.out.println("StaticDemo.y 2 = " + StaticDemo.y);
}

Answer 1

You can only have one main method. Try something like this:
class StaticDemo
   int x;
   static int y;
class Demo
   public static void main(String[] args) {
      StaticDemo.y = 30;
      System.out.println("StaticDemo.y = " + StaticDemo.y);
      Demo2 d2 = new Demo2();
      d2.display();
class Demo2
   void display() {
      System.out.println("StaticDemo.y 2 = " + StaticDemo.y);