Top 6 AI and Prompt Engineering Books for Software Engineers in 2025

Hello guys, AI and Large Language Models (LLMs) are transforming the software engineering landscape. While many developers use tools like ChatGPT or GitHub Copilot, understanding the engineering principles behind them is essential to stay relevant in 2025 and beyond.  While there are many resources to learn about AI Engineering, Prompt Engineering and LLM Engineering, and I have also shared online courses and roadmap, books offer structured and in-depth learning that videos and blogs often lack. They are often created by true experts and authorities who have done a lot of research in that area and that's why I always include book in my learning process.

How to use ConcurrentHashMap in Java - Example Tutorial and Working

ConcurrentHashMap in Java is introduced as an alternative of Hashtable in Java 1.5 as part of the Java concurrency package. Prior to Java 1.5 if you need a Map implementation, which can be safely used in a concurrent and multi-threaded Java program, then, you only have Hashtable or synchronized Map because HashMap is not thread-safe. With ConcurrentHashMap, now you have a better choice; because not only it can be safely used in the concurrent multi-threaded environment but also provides better performance over Hashtable and synchronizedMap.

How to use EnumSet in Java with Example

EnumSet is one of the specialized implementations of the Set interface for an enumeration type, introduced in Java 1.5 along with the enumeration type itself. Programmer often stores Enum into common collection classes e.g. HashSet or ArrayList, mostly because they are unaware of this little gem. Even I wasn't aware of this class a few years ago until I come across one of the finest books for Java programmers, Effective Java. It has an Item on EnumSet, which highlights some typical use-cases for this collection class instead of using int variable and bitwise operator. Since Enum constants are unique and have pre-defined lengths, as you can not define a new enum constant at runtime; it allows Java API designers to highly optimize EnumSet.

What is difference between Enumeration and Iterator in Java? Answer

Though both Iterator and Enumeration allows you to traverse over elements of Collections in Java, there is some significant difference between them e.g. Iterator also allows you to remove elements from the collection during traversal but Enumeration doesn't allow that, it doesn't get remove() method. Enumeration is also a legacy class and not all Collection supports it e.g. Vector supports Enumeration but ArrayList doesn't. On the other hand, Iterator is the standard class for iteration and traversal. By the way,  what is the difference between Enumeration and Iterator in Java? 

Top 11 Java ConcurrentHashMap Interview Questions with Answers [UPDATED]

The ConcurrentHashMap class part of concurrent collections package added on JDK 1.5 which contains utility classes like BlockingQueue, CopyOnWriteArrayList, CopyOnWriteArraySet etc. It is a replacement of synchronized hash-based map implementations e.g. Hashtable and synchronized HashMap. It implements Map and ConcurrentMap (a sub-interface of Map) interface which allows you to store key-value pairs. The class is similar to HashMap or Hashtable but it's more scalable and the right fit for concurrent Java application. Unlike Hashtable which achieves its thread-safety by compromising the scalability, ConcurrentHashMap uses advanced techniques e.g. dividing the map into segments to remain thread-safe and scalable at the same time.

How HashMap works in Java?

Hello guys, if you are looking for an answer of popular Java interview question, how HashMap works in Java? or How HashMap works internally in Java then you have come to the right place. In this article, I will not just answer those question but also many related questions like How get() and put() method works in Java? what role equals() and hashcode() play in HashMap, How HashMap resize itself, and why key object of HashMap should be Immutable in Java. Let's start with the basics first. HashMap in Java works on hashing principles. It is a data structure that allows us to store object and retrieve it in constant time O(1) provided we know the key. Also this is one of my most popular article with more than 6 million views and I have now updated it to include latest information like how HashMap now uses a balanced tree instead of linked list for storing collision objects and new diagrams on HashMap working which provide visual explanations. 

Difference between fail-safe vs fail-fast Iterator in Java? Example

The difference between fail-safe and fail-fast Iterator is becoming favorite core java interview questions day by day, the reason it touches concurrency a bit, and the interviewee can go deep on it to ask how fail-safe or fail-fast behavior is implemented. In this article, we will see what are fail-safe and fail-fast iterators in java and the differences between fail-fast and fail-safe iterators. The concept of the fail-safe iterator is relatively new in Java and was first introduced with Concurrent Collections in Java 5 like ConcurrentHashMap and CopyOnWriteArrayList.

Difference between List and Set in Java Collection? Example

What is the difference between List and Set in Java is a very popular Java collection interview question and an important fundamental concept to remember while using the Collections class in Java. Both List and Set are two of the most important Collection classes Java Program use along with various Map implementations. The basic feature of List and Set are abstracted in the List and Set interface in Java and then various implementations of List and Set adds specific features on top of that e.g. ArrayList in Java is a List implementation backed by Array while LinkedList is another List implementation that works like linked list data-structure.

Difference between ArrayList and Vector in Java

ArrayList and Vector are two of the most used classes on the java collection package and the difference between Vector and ArrayList is one of the most frequently asked java interview questions on first-round or phone interviews. Though it’s quite a simple question in my opinion but knowledge of when to use Vector over ArrayList or does matter if you are working on a project. In this article, we will some point-based differences between Vector and ArrayList in Java and trying to understand the concept behind those differences. 

What is difference between HashMap and Hashtable in Java?

HashMap vs Hashtable in Java
Though both Hashtable and HashMap are data-structure based upon hashing and implementation of Map interface, the main difference between them is that HashMap is not thread-safe but Hashtable is thread-safe. This means you cannot use HashMap in a multi-threaded Java application without external synchronization. Another difference is HashMap allows one null key and null values but Hashtable doesn't allow null key or values. Also, the thread-safety of the hash table is achieved using internal synchronization, which makes it slower than HashMap.

Difference between LinkedList and ArrayList in Java

LinkedList and ArrayList both implement List Interface but how they work internally is where the differences lie. The main difference between ArrayList and LinkedList is that ArrayList is implemented using a resizable array while LinkedList is implemented using doubly LinkedList. ArrayList is more popular among Java programmers than LinkedList as there are few scenarios on which LinkedList is a suitable collection than ArrayList. In this article, we will see some differences between LinkedList and ArrayList and try to find out when and where to use LinkedList over ArrayList.

Difference between TreeSet, LinkedHashSet and HashSet in Java with Example

TreeSet, LinkedHashSet, and HashSet all are implementation of the Set interface and by virtue of that, they follow the contract of Set interface i.e. they do not allow duplicate elements. Despite being from the same type of hierarchy,  there are a lot of differences between them; which is important to understand, so that you can choose the most appropriate Set implementation based upon your requirement. By the way difference between TreeSet and HashSet or LinkedHashSet is also one of the popular Java Collection interview questions, not as popular as Hashtable vs HashMap or ArrayList vs Vector but still appears in various Java interviews.

Difference between PriorityQueue and TreeSet in Java? Example

The PriorityQueue and TreeSet collection classes have a lot of similarities e.g. both provide O(log(N)) time complexity for adding, removing, and searching elements, both are non-synchronized and you can get elements from both PriorityQueue and TreeSet in sorted order, but there is a fundamental difference between them, TreeSet is a Set and doesn't allow a duplicate element, while PriorityQueue is a queue and doesn't have such restriction. It can contain multiple elements with equal values and in that case head of the queue will be arbitrarily chosen from them.

Difference between Synchronized and Concurrent Collections in Java? Answer

Synchronized vs Concurrent Collections
Though both Synchronized and Concurrent Collection classes provide thread-safety, the differences between them come in performance, scalability, and how they achieve thread-safety. Synchronized collections like synchronized HashMap, Hashtable, HashSet, Vector, and synchronized ArrayList are much slower than their concurrent counterparts like ConcurrentHashMap, CopyOnWriteArrayList, and CopyOnWriteHashSet. The main reason for this slowness is locking; synchronized collections lock the whole collection e.g. whole Map or List while concurrent collection never locks the whole Map or List.

How to choose the Right Collection Class in Java? List, Set, Map, and Queue Example

The Java collection framework offers implementation of different data structure like an array, list, set, map, queue, tree, etc and the choice really depends upon the situation and properties of the different data structure. For example, if your requirement is fast search with index then you can use ArrayList and if you want to store key-value pairs then you would consider using hash table data structure and there are a couple of implementation of hash table data structure in Java, like HashMap, Hashtable, LinkedHashMap, TreeMap, and ConcurrentHashMap. Now, which one will you choose? If you don't know or confused don't worry, I will give you a set of rules and use cases which will help you choose the right Collection type in Java depending upon scenario.