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Difference between a List and ArrayList Reference Variable in Java?

Someone who is just starting with Java programming language often has doubt about how we are storing an ArrayList object in List variable, what is the difference between List and ArrayList? or why not just store the ArrayList object in ArrayList variable just like we do for String, int, and other data types. Well, the main difference between List and ArrayList is that List is an interface while ArrayList is a class. Most importantly, it implements the List interface, which also means that ArrayList is a subtype of List interface. In Java or any object oriented language, super type of variable can store an object of subtype. This is known as Polymorphism because any virtual method will be executed from subclass only, even though they were called from super type. This is the beginning, now let's see those two questions as well.

How to Compare Two Dates in Java? Check If They Are Equal, Later or Earlier

There are multiple ways to compare two dates in Java, it also depends on upon what exactly comparison means. If you are looking to compare two dates to find out whether they are equal or not, then you can simply use equals() method of java.util.Date class. This method will return true if both dates are equal, precisely both thave same millisecond value. If you are looking to find out whether a date comes before or after another date then you have 3 choices, you can use compareTo() method of java.util.Date class, or you can use before() and after() method of Date class, or you can use before() and after() method of Calendar class. I suggest leveraging before() and after() method of Date class, they are more readable and easy to use.

Java - InstanceOf KeyWord Example and Tutorial

The Java programming language and JVM are full of hidden gems and even though I am using Java for more than a decade I still get surprised of features which I didn't know for quite some time e.g. shutdown hook, covariant method overriding, and JVM option to refresh DNS cache.  The instanceof operator is also one of the rarely known features of Java, It is used to check if an object is the instance of a particular Class or not. It returns true if the object is an instance of the class, otherwise, returns false. You might have seen usages of instanceof operator in Java while overriding equals() method. Since for checking equality of two instances, the first step is to verify whether they are the instance of the same object or not, you can use the instanceof operator there.

Top 50 Basic Core Java Interview Questions with Answers

If you are preparing for your next Core Java interview and looking for some common question to practice or check your knowledge then you have come to the right place. In this article, I'll share 50 Core Java Interview Questions from various companies. I have already discussed the answers to these questions in this blog or Javarevisited, so I have just put the link. First, you should try to answer it yourself and if you cannot then go to the link and find the answer. You can also compare your answer with mine and learn a few things here and there. In most of my interview post, I have also shared some common techniques to drive interview towards your comfort zone and how to leave a long-lasting impression on the interviewer, you can use those techniques to do well on your Java interviews.