10 Best Practices for Handling Null in Java

Hello guys, Dealing with null is an inevitable part of Java programming, but following best practices can help you manage it effectively and write more reliable code. In this article, we'll explore ten best practices for handling null in Java to improve code quality and avoid common pitfalls. If you can handle null then you will sure write better code as null is often the cause of Runtime errors in Java, you may heard of NullPointerException? No. If not then I can say that you have not coded enough in Java because it was the first error I got when I start writing Java program in my college days. At that time I don't know how to handle null better so it's long painful debugging until we find the cause and then do some workaround or fix but if you know how to handle null better then you can write code which can withstand test of time in production. 

How to remove given character from String using Recursion and Iteration in Java? Coding Interview Question

Hello guys, in the past, I have discussed several popular and frequently asked Java programs from interviews and coding interview questions and today, I am going to share another popular String based coding interview question for Java developers. The questions goes as - write a method to remove all occurence of a given character from String in Java, you can not use a library method like replace() or remove() which can solve the problem for you. You have to build the logic by yourself. You have to provide both iterative and recursive solution of this question. Along with that, you have to provide some unit test as well, which you can write using JUnit or TestNG testing framework. 

Polymorphism and Open Closed Design Principle Example in Java

Java is an object-oriented programming language that allows developers to create complex software applications by organizing code into objects. One of the key features of object-oriented programming is Polymorphism. Polymorphism refers to the ability of objects to take on different forms, depending on the context in which they are used. In Java, polymorphism is achieved through two mechanisms: inheritance and interfaces. In this blog post, I will explain what polymorphism is in Java, how it works, and provide examples to illustrate its usage. We will also discuss the benefits of using polymorphism in your Java programs, as well as some best practices for implementing it effectively.

Java 8 Stream.filter() example Example with Null and Empty String

The filter() is a method on Stream class, which accepts a Predicate (a functional interface with a method which return boolean) and returns a stream consisting of the elements of this stream that match the given predicate. For example, if stream is obtained from a list containing "SONY", "APPLE" and "GOOGLE" and predicate is elements with length greater than 4, then filter will return another stream containing only APPLE and GOOGLE, leaving SONY out because its length is not greater than 4. Java 8 provides advanced filtering capability using lambdas and predicates. 

How to Create and Extract a ZIP File in Java? Unzip Example Tutorial

In Java, you can use ZipFile class to unzip a .jar and .zip file in Java. These classes are defined in and java.util.zip package. Unfortunately there is no ZipUtil class, which provides straightforward methods to decompress zip files, but thankfully there are enough tools available in JDK to write your own method to extract zip file in Java. There are mainly two steps to unzip a zip file in Java, first, create all directories inside of the zip file, because zip archive flattens all directory and second create all file which are inside .zip file. Sinze files in .zip file is not in specific order, you need to iterate twice to perform these steps individually.

Why is Java Considered a Secure Programming Language?

Hello guys, Security is a paramount concern in software development, and choosing the right programming language can play a crucial role in mitigating potential vulnerabilities and threats. Java has long been celebrated for its security features and practices, making it a preferred choice for building secure applications and systems. In this article, we'll explore why Java is considered a secure programming language and examine the features and practices that contribute to its security reputation.

Difference between Queue and Deque in Java? Example Tutorial

Hello guys, today I am going to share another interesting question from Java interview, what is difference between Queue and Deque in Java. This question was asked to one of my reader in a recent interview with JP Morgan Mumbai and this is also a popular Java collection interview question. While he was able to answer the question, he wasn't able to convince interviewer so he asked me how to answer this question. So I am writing this post to share my answer on Queue vs Deque in Java. In the vast world of Java programming, the need to manage data efficiently often leads developers to specialized data structures. 

How to find length/size of ArrayList in Java? Example

You can use the size() method of java.util.ArrayList to find the length or size of ArrayList in Java. The size() method returns an integer equal to a number of elements present in the array list. It's different than the length of the array which is backing the ArrayList, which is called the capacity of ArrayList. When you create an object of ArrayList in Java without specifying a capacity, it is created with a default capacity which is 10. Since ArrayList is a growable array, it automatically resizes when the size (number of elements in the array list) grows beyond a threshold. 

How to remove all elements of ArrayList in Java - RemoveAll Example

There are two ways to remove all elements of an ArrayList in Java, either by using clear() or by using the removeAll() method. Both methods are defined in the java.util.List and java.util.Collection interface, hence they are available not just to ArrayList but also to Vector or LinkedList, etc. Both elements remove all objects from ArrayList but there is a subtle difference in how they do. The clear() method is straightforward, it traverses through the ArrayList and sets all indices to null, which means the ArrayList becomes empty and all elements become eligible to Garbage collection, provided there are no more references to them.

How to loop over a TreeSet in Java with Example

In our earlier articles, we have learned how to loop over ArrayList in Java and you can use the same logic to loop over a TreeSet. You can use both, enhanced for loop and Iterator to traverse over TreeSet in Java. Though worth noting is that Iterator returned by the iterator() method of TreeSet returns elements in the sorted order which is imposed by the Comparator you have provided to TreeSet at the time of instantiation. By default, if you don't provide any custom Comparator then TreeSet sorts elements in their natural order like String elements are sorted in alphabetical order and Integer elements are sorted in numeric order. When you iterate over a TreeSet the iterator follows this order.

How to Convert Vector to Array in Java? 2 Examples

In the last article, we have learned how to convert a LinkedList to an array in Java, and in today's tutorial, you will learn how to convert a Vector to an array in Java. There is a similarity between Vector and LinkedList, both implement the List interface. Even though Vector is a legacy class and exists in Java from JDK 1.1 long before the Java Collection framework was introduced, it was later retrofitted to implement the List interface. You can use the same toArray() method to convert a Vector to an array in Java. 

How to sort a LinkedList in Java? Example Tutorial

Since LinkedList implements the java.util.List interface, you can sort the LinkedList by using the Collections.sort() method, just like you sort an ArrayList. Since the LinkedList class implements the linked list data structure which doesn't provide random access based upon the index, sorting is quite expensive. In order to access any element, you need to first traverse through that element which is the O(n) operator. This method uses an efficient strategy to handle this scenario. It first copies the contents of LinkedList to an array, sorts the array, and copies it back. 

10 Example of List in Java

Hello guys,  Java, as a versatile and widely used programming language, offers a plethora of data structures to developers. One of them is List which is also fundamental component in Java's collection framework, play a pivotal role in managing and manipulating sequences of elements. In the past, I have shared 10 Examples of HashMap in Java and In this article, we'll delve into Java lists, exploring their features and providing ten illustrative examples to deepen your understanding. List are also a popular topic from Java interviews with questions like difference between ArrayList and LinkedList which have been asked to me almost 10 times in past 20 years. 

How to Convert a List to a Set in Java with Example

How to convert a List to Set in Java

Many times we need to convert one collection to another like converting a List to a Set. It's also an easy way to copy contents from one collection to other in Java, like from List to Set or Set to List. Thanks to the Collection framework in Java, copying collections from one to another is extremely easy. Since every Collection class implements a Collection interface that defines the addAll() method, which can be used to create a collection from contents of another collection.

Difference between ArrayList and HashMap in Java

Difference between ArrayList and HashMap in Java
One of the most critical differences between the HashMap and ArrayList class is that the former is the implementation of the hash table while the latter is a dynamic array that can resize itself. The HashMap and ArrayList are two of the most popular classes from the Java Collection framework. Though both are used to store objects they are completely different in their implementation, working, and usage. The main difference between ArrayList and HashMap is that ArrayList is an index-based data structure backed by an array while HashMap is a map data structure that works on hashing to retrieve stored values. 

How to sort HashSet in Java? Example

Somebody asked me recently, how do you sort a HashSet? For lists, we use the Collections.sort(List) method, but there is nothing for Set. If I have a HashSet then how would I go about sorting it? The answer is you cannot sort a HashSet, why? because HashSet is an unordered collection. When you insert an element in HashSet then you lose the order guarantee. You cannot do reordering or sorting in Set because it does not have random access methods (ie, .get() an element at a given index), which is basically required for sort algorithms.

How to declare ArrayList with values in Java? Examples

Sometimes you want to create an ArrayList with values, just like you initialize t at the time of declaration, as shown below:

int[] primes = {2, 3, 5, 7, 11, 13, 17};
or
String[] names = {"john", "Johnny", "Tom", "Harry"};

but unfortunately, ArrayList doesn't support such kind of declaration in Java. But don't worry, there is a workaround to declare an ArrayList with values e.g. String, integers, floats, or doubles by using the Arrays.asList() method, which is nothing but a shortcut to convert an Array to ArrayList.

How to add element at first and last position of linked list in Java? Example Tutorial

LinkedList class in java.util package provides the addFirst() method to add an element at the start of the linked list (also known as head)  and addLast() method to add an element at the end of the linked list, also known as the tail of the linked list. Java's LinkedList class is an implementation of a doubly linked list data structure but it also implements java.util.Deque interface and these two methods came from that interface, which means they are only available from Java 1.6 onward. addFirst() method insert the specified element at the beginning of the linked list and addLast() method insert the specified element at the end of the linked list.

Difference between Class and Record in Java?

Hello guys, when it comes to defining data structures in Java, two primary options are at your disposal: records and classes. Each has its unique characteristics and use cases, and understanding the differences between them is crucial for making the right design choices in your Java applications. This has now also become a popular Java interview question and asked to one of my reader recently as well.  Java classes have been the cornerstone of object-oriented programming for years, offering full customization and flexibility. They allow you to define complex objects with custom behavior, encapsulation, and fine-grained control over state changes.

Difference between HashMap and LinkedHashMap in Java

Difference between LinkedHashMap and HashMap in Java
HashMap and LinkedHashMap are two of the most commonly used Map implementation in Java. The main difference between HashMap and LinkedHashMap is that LinkedHashMap maintains the insertion order of keys, the order in which keys are inserted into LinkedHashMap. On the other hand, HashMap doesn't maintain any order or keys, or values. In terms of performance, there is not much difference between HashMap and LinkedHashMap but yes LinkedHashMap has more memory footprint than HashMap to maintain doubly LinkedList which it uses to keep track of the insertion order of keys.