Java Programming - Language Fundamentals - Discussion

Dog is a class and why the object has been created like that?

But Dog is a class. And if we want to create an array fo object we need only one subcript.

Why array didn't initialized automatically?

Why not compilation fails?

public class Test
{
public static void main(String [] args)
{
int [][] theDogs = new int[2][];
System.out.println(theDogs[1][0]);
}
}

The above program will give throw the same Exception NullPointer because we have only declared an array and not initialized it.

Now check the below program i.e. after initializing the array.

public class Test . This code will print the value 3
{
public static void main(String [] args)
{
int [][] theDogs = new int[][] {{1,2},{3,4}};
System.out.println(theDogs[1][0]);
}
}

Dog [][] the Dogs = new Dog[3][];

The Dogs[2] = new Dog[7]; // Initialize the 3rd row of the Dogs 2D array.

The Dogs[2][0] = new Dog (); // Initialize the Dog instance at the 1st column of the 3rd row.

System.out.println (the Dogs[2][0].toString ()); // Now you can execute methods of the Dogs[2][0].

Dog[][] the Dogs = new Dog[3][];

Should be replaced by int Dog[][] the Dogs = new Dog[3][any no.];

Can anyone explain that what's the solution of this problem.

In the above program we have initialized just first column not second one. So we are getting null pointer exception.

Though we have

Dog [][] theDogs = new Dog[3][];

This comment is an uninitialized array of "Objects"

If you recall that an uninitialized object contain null pointer which actually points to nothing.

Hence the Exception.