Why one argument constructor is added when no argument constructor is provided [BillPaughSingleTon]?

I was trying to break BillPaugh Singleton solution using reflection, well I am able to do it but I can see two constructors while accessing the BillPaughSingleTon solution. Why so ? Also by trial and error found that the line inside HelperClass is causing this. Again why so ?

BillPaughClass

package creational.BillPaugh;

public class SingleTonBillPaugh
{
  private SingleTonBillPaugh instance;

  public static SingleTonBillPaugh getInstance()
  {
    return SingleTonHelper.instance;
  }

  private SingleTonBillPaugh()
  {
    System.out.println(Thread.currentThread().getName() + " instance is going to be created");
  }

  static class SingleTonHelper
  {
    private static final SingleTonBillPaugh instance = new SingleTonBillPaugh(); //if we remove this line, multiple constructor will not be there. But this line is needed for singleton. 
  }
}

Breaking SingleTon using Reflection .

package creational.BillPaugh;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

public class BreakBillPaughUsingReflection
{
  public static void main(String[] args)
  {

    SingleTonBillPaugh singletonInstance1 = SingleTonBillPaugh.getInstance();
    System.out.println("singletonInstance1 " + singletonInstance1);

    SingleTonBillPaugh singletonInstance2;
    Constructor[] constructors = SingleTonBillPaugh.class.getDeclaredConstructors();

    for (Constructor construct : constructors)
    {
      construct.setAccessible(true);
      try
      {
        singletonInstance2 = (SingleTonBillPaugh) construct.newInstance();
        System.out.println("singletonInstance2 " + singletonInstance2);
      }
      catch (InstantiationException | IllegalAccessException | IllegalArgumentException
        | InvocationTargetException e)
      {
        e.printStackTrace();
      }
    }// end for

    Constructor[] constructors2 = NormalClass.class.getDeclaredConstructors();

  }
}

Proof of two constructor.