Why Array doesn't have Class file? Still we can create an array object without class file also

Hi,

I would like to let you know about arrays in java.

I have observed so many developers, when I ask to solve below problem they get confused and tell the wrong answer.

int[] a={1, 2, 3};
int[] b={1, 2, 3};

System.out.println(a.equals(b));
O/P= ?

They say true as answer which is a wrong answer.

Immediately I will ask them for explanation. They say both arrays are have same content so JVM checks for content to check the equality.

Then the next question will be what is the use of equals() method....

Explanation why the answer is false:

If we observe the java API. There is no direct class file to create object of type Array.

Whenever you execute above statements JVM internally creates a memory space based on its size and returns the reference to you. It means that there is no class to create object using new operator.

And if you check that object is the instance of Object class. It will show true.

It means, as per java standards any object you create for any class that objects parent object will be always Object only.

Here any kind of array created by JVM is the single level object in hierarchy of the object view. It means the immediate supper class always will be Object only.

You know what is there in Object class's equals() method..

And here in array object there is no implementation for equals() method. If the implementation is really there then we would have the class to create object.

So, whenever you execute above statements there will be two different objects even though they have same content in it and equals() method will be called of Object class object which will check for hashcode equality...

That's why you get false as output. :)

Hint: There is a separate assertion method available in junit to check the equality of two arrays...

Please give your feedback: nagarjuna.lingala@gmail.com

Usage of Vagrant along with Virtualbox

Hi All,

I already used virtualbox earlier. But recently I got a chance to work on it again. But here the usage style it's different. :)

Basically the thing is, we use virtualbox to run another operating system on the current OS. But as a normal user, we expect the UI from it.

As a developer, sometimes we don't require the UI instead we go for services from it. This time how do we run a virtual OS.

Virtualbox developers provided some command line utilities to achieve these kind of things.

But there will be a requirement to play with multiple operating systems virtually.

Here one tool helps us to do in that way...

That tool name is vagrant. It is really awesome to work with virtual operating systems. And no need to interact with the virtualbox directly. There will be a central configuration file for vagrant.

But the vagrant requires virtualbox :) i.e Vagrantfile

We can define which service port numbers of host OS to be routed to which ports of Guest OS.