Array question from certpal

[Surender Suri]

what does this array declaration mean ? a string array of 5 with each size of size 5 elements ?

public class ID  
{
    public static void main(String... args)
    {
        Object [] object = new String[5][5];
        int counter=0;
        for (Object o : object )
        {
            counter++;
        }
        System.out.println(counter);
    }
}

[gurpeet singh]

Object [] object = new String[5][5];

object is a reference variable of type Object array. now this object reference variable refers to a CONTAINER with 5 elements of type Object. each of the 5 references of the type Object points to a String array with five elements. this is possible because a reference of type Object can refer to any object, hence it is able to refer to String array. even if you do Object object = new String[5][5] it would be compile.

[Surender Suri]

Thanks gurpeet. One more Q.

how is the answer 1 here ? it should be "devil boast devil boast" right ? or i am missing something ..

public class Toast extends Boast 
{
    Integer eye=1;
    public static void main(String... args)
    {
        Toast eye = new Toast(); 
        new Devil(eye).honey(eye);
        new Boast(eye).honey(eye);
        new Toast().honey(eye);
    }
    public void honey(Toast eye)
    {
        eye.eye = new Integer(-2);
    }    
    
}

class Boast extends Devil 
{
    public Boast(){System.out.print("boast ");}
    public Boast(Toast eye)
    {
        eye.eye = new Integer(5);
    }
    
    public void honey(Toast eye)
    {
        eye.eye = new Integer(2);
    }
}

class Devil
{
    public Devil(){System.out.print("devil ");}
    public Devil(Toast eye)
    {
        eye.eye = new Integer(1);
    }
    public void honey(Toast eye)
    {
        eye.eye = new Integer(9);
    }    
}

1.) devil boast devil devil boast - Answer

2.) devil boast devil boast devil boast devil boast

3.) devil boast devil devil boast devil boast

4.) Runtime error

5.) None of the above

[gurpeet singh]

correct answer is A only. you are missing a very small part. just a hint and try for yourself. what happens when you create new Boast(eye) object. ? what is the sequence ?

post if you got the answer.

[Surender Suri]

got it .. Boast(eye) calls the default no-arg constructor of Devil class .. i was thinking it will call Devil(eye) .. but that would require a explicit call to super(eye) ... humm.. what was i thinking :-) thanks gurpeet

this is what happens when you drink beer and take test :-)

[gurpeet singh]

welcome. they show opposite in movies. in the social network they showed zuckerberg drinking beer and hacking 20+ sites during night. wonder if he really did in real

[Karthikeyan Kandasamy]

Hi,

I still could not understand the 1st question / answer.

Object [] object = new String[5][5];

If i try the following (assignment to String array reference), am getting a compiler error. Why is the special consideration for object array reference variable?.

String [] str = new String[5][5];

Compiler Error:
------------------
arrays\ArrayDeclarations.java:10: incompatible types
found : java.lang.String[][]
required: java.lang.String[]
String [] str = new String[5][5];
^
1 error

[gurpeet singh]

the special consideration is because of the fact that a reference of the type Object can refer to anything.

forget any of above . consider this

Object obj = new String[5][5];

above will compile because of the simple reason that obj is of the type Object which can ofcourse refer to objects of the type Object. since arrays are one of them(i.e. objects) it can refer to them.

when you write Object [] obj = new String[5][5]; this is just an extension of above thing. here you have an array of references of the type Object each of which are able to refer to string array

String [] str = new String[5][5]; here you have a str which is of the type String array . it points to a container which contains references of the type String which must refer to string array which of course is not possible.

[Karthikeyan Kandasamy]

Thanks Gurpeet. I got it now.