Thursday, August 28, 2014

Quicksort Sorting Algorithm in Java

Quicksort algorithm is one of the most used sorting algorithm, especially to sort large list and most of the programming languages, library have implemented it in one or another way. In Java, Arrays.sort() method sorts primitive data types using double pivot Quicksort algorithm, authored by Joshua Bloach and others. This implementation provides better performance for lot of data sets, where traditional quicksort algorithm reduced into quadratic performance. This method also uses MergeSort, another good sorting algorithm, to sort objects. QuickSort implementations are also available in C++ STL library. Have you ever thought why quicksort is so popular? because on average it is one of the fastest sorting algorithm we have. On average quicksort is a O(n log n) algorithm, while it's worst case is O(n^2), which is much better comparing with Bubble Sort or Insertion Sort. It's also one of the popular algorithm interview question, so as a programmer you must know how QuickSort works as well as how to implement Quicksort in Java or any other programming language. One of the most important thing interviewer look in your quicksort implementation is choice of pivot and whether you are sorting in place or not. In "in-place" sorting, actual sorting takes place in same array and no additional space is needed. Due to this reason, quicksort is very efficient in sorting large list of numbers, as no additional memory is required, a very space efficient sorting algorithm. Quicksort is also one of the naturally recursive algorithm and serves a good exercise for Java programmers to master art of recursion.

Tuesday, August 26, 2014

2 Examples to Convert Byte[] array to String in Java

Converting a byte array to String seems easy but what is difficult is, doing it correctly. Many programmers make mistake of ignoring character encoding whenever bytes are converted into a String or char or vice versa. As a programmer, we all know that computer's only understand binary data i.e. 0 and 1. All things we see and use e.g. images, text files, movies, or any other multi-media is stored in form of bytes, but what is more important is process of encoding or decoding bytes to character. Data conversion is an important topic on any programming interview, and because of trickiness of character encoding, this questions is one of the most popular String Interview question on Java Interviews. While reading a String from input source e.g. XML files, HTTP request, network port, or database, you must pay attention on which character encoding (e.g. UTF-8, UTF-16, and ISO 8859-1) they are encoded. If you will not use the same character encoding while converting bytes to String, you would end up with a corrupt String which may contain totally incorrect values. You might have seen ?, square brackets after converting byte[] to String, those are because of values your current character encoding is not supporting, and just showing some garbage values.

Tuesday, August 19, 2014

15 Java NIO, Socket, and Networking Interview Questions Answers

Networking and Socket Programming is one of the important area of Java programming language, especially for those programmers, who are working in client server based applications. Knowledge of important protocols e.g. TCP and UDP in detail is very important, especially if you are in business of writing high frequency trading application, which communicate via FIX Protocol or native exchange protocol. In this article, we will some of the frequently asked questions on networking and socket programming, mostly based around TCP IP protocol. This article is kinda light on NIO though, as it doesn't include questions from multiplexing, selectors, ByteBuffer and FileChannel but it does include classical questions like difference between IO and NIO. Main focus of this post is to make Java developer familiar with low level parts e.g. how TCP and UDP protocol works, socket options and writing multi-threaded servers in Java. Questions discussed here is not really tied up with Java programming language, and can be used in any programming language, which allows programmers to write client-server applications. By the way, If you are going for interview on Investment banks for core Java developer role, you better prepare well on Java NIO, Socket Programming, TCP, UDP and Networking along with other popular topics e.g. multi-threadingCollections API and Garbage Collection tuning. You can also contribute any question, which is asked to you or related to socket programming and networking and can be useful for Java interviews.