예제를 통한 생성자의 이해

package day07;
public class P306 {
	public static void main(String[] args) 
	{
		
		Product a  =  new  Product(); 
		Product a1 = new Product(); 
		Product a2 = new Product(); 
		Product a3 = new Product(); 
		Product a4 = new Product(); 
		System.out.println(a.serialNum);
		System.out.println(a1.serialNum);
		System.out.println(a2.serialNum);
		System.out.println(a3.serialNum);
		System.out.println(a4.serialNum);
		
		
		
	}
}
class Product 
	{
		// 기본 생성자 생성 ( Produc a = new Product(); ) 
		static int count;
		int serialNum;
		{
			count ++;
			serialNum = count;
		}
		Product(){
		}	
	}