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Difference between Abstract class and Interface in Java 8

Ever since JDK 8 has allowed concrete (non-abstract) methods on the interface like default and static methods, many of my readers have asked me how should they answer the classical abstract class vs interface questions. Earlier, an interface cannot have any concrete methods and that was the main difference between abstract class and interface but now that is not the case. In this post, I'll revisit this hugely popular Java interview question in light of Java 8 changes. As I said, before JDK 8, the level of abstraction was the clear-cut difference between abstract class and interface i.e. interface was the purest form of abstraction which only defines what interface is supposed to do without specifying how they should be implemented, in other words, it only declares API methods and leaves implementation to its subclasses.

Top 10 Java 8 Stream and Functional Programming Interview Questions Answers

The JDK 8 release has changed the way we write Java. With new functional programming idioms and a powerful Stream API, most of the new Java code is written in functional style. This also means that Stream and Functional programming related questions are increasing on Java interviews. If you are not familiar with Java 8 changes then it's difficult to crack a Java interview nowadays. Though it's not stated anywhere most of the companies now expect Java developers to know at least Java 8, which is also good right? Java 11 is already out and we are looking forward to Java 12 in a couple of months, it makes sense to know at least Java 8 changes.  Since more and more of my readers are asking about Java 8 interview questions to me, I have started a series where I take one or two topics and share 15 to 20 interview questions.

Java - String charAt Example - How to get first and last characters

The charAt(int index) method of java.lang.String class can be used to retrieve a character from given index. The method returns a character, you can see its return type is char. The index starts from zero and ranges to length() - 1 where length() return the length of String. It's similar to an array where the first element is stored at zeroth index and the last element is stored at length -1 index because String is nothing but backed by a character array. If the value of the index is invalid i.e. it's lower than zero or negative or higher than length - 1 then this method throws an IndexOutOfBoundsException. In this article, I'll show you a couple of example of how to use the charAt() method to retrieve a character from String in Java.