// This program checks the default values of various variables
// Define a class with lots of variables for posterioty sake

class Lotsavar{
    int num;
    double val;
    String name;
    Lotsavar cls;
}

public class defValue {
    
    public static void main(String[] args) {
	int n;
	double v;
	boolean a;
	String s;
	String s1=new String();
	
	// These prints will be illegal now since s and n don't point to
	// anything yet. In a box diagram, this will be represented by
	// `?' rather than null or 0  
	
	// System.out.println("Print statement#1 "+ n);
	// System.out.println("Print statement#2 "+ s);
	
	// This print statement is legal but observe what it prints
	
	System.out.println("Print statement#3 "+s1);
	
	// Lotsavar is a class with lot of variables(see above)
	
	Lotsavar obj1,obj2;
	
	// obj1, obj2 not yet initialized, so you can't do this...
	// System.out.println("Print statement#4 "+ obj1.num);
	
	// So initialize them first
	obj1=new Lotsavar(); obj2=new Lotsavar();
	
	// Now you can use them. Default values appear
	
	System.out.println("Print statement#5 "+ obj1.num);
	System.out.println("Print statement#6 "+ obj1.val);
	System.out.println("Print statement#7 "+ obj2.val);
	System.out.println("Print statement#8 "+ obj1.name);
	System.out.println("Print statement#9 "+ obj2.name);
	
	// Now change some instance variables from their default
	
	obj1.num=30;obj1.val=0.33;obj1.name="Whatever";
	
	System.out.println("Print statement#10 "+ obj1.num);
	System.out.println("Print statement#11 "+ obj1.val);
	System.out.println("Print statement#12 "+ obj2.val);
	System.out.println("Print statement#13 "+ obj1.name);
	System.out.println("Print statement#14 "+ obj2.name);
	
	obj1.cls=obj2;
	
	System.out.println("Print statement#15 "+ obj1.cls.num);
	System.out.println("Print statement#16 "+ obj1.cls.val);
	System.out.println("Print statement#17 "+ obj1.cls.name);
	System.out.println("Print statement#18 "+ obj2.name);
	
	// System.out.println("Print statement#19 "+ obj2.cls.val);
	// Since obj2.cls is still null, a reference such as above
	// leads to run time error:
	// Exception in thread "main" java.lang.NullPointerException
	
    }
}