Is main is mandatory

Hello,

   I came across a java code which reads as below in this there is no main part and still the code gets compiled and works.  My question is that is main is mandatory for each and every program if not on what logic does the compiler will interpret those programs which has no main.  And also can anyone tell me how to create array of handle for objects with a simple example.

The code goes here
-------------------
class gg {
  private gg() {}
  // (1) Allow creation via static method:
  public static gg makeSoup() {
    return new gg();
  }
  // (2) Create a static object and
  // return a reference upon request.
  // (The "Singleton" pattern):
  private static gg ps1 = new gg();
  public static gg access() {
    return ps1;
  }
  public void f() {}
}

class Sandwich { // Uses Lunch
  void f() { new Lunch(); }
}

// Only one public class allowed per file:
public class Lunch {
  void test() {
    // Can't do this! Private constructor:
    //! gg priv1 = new gg();
    gg priv2 = gg.makeSoup();
    Sandwich f1 = new Sandwich();
    Soup.access().f();
  }
}
-----------------------------------------

Thank u in advance,
nature