In this tutorial, we will be going through the installation process of Maven. If you are a WINDOWS user (if you are not, scroll down to view how to install Maven if you are a Linux or Mac user): Before proceeding with the next steps, make sure you have JDK installed on your system. If…
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Simply said, Maven profile is a set of configuration value which override default values. By using it, it allows you to create a custom build for different environments (Production/Development). Before we proceed with the tutorial’s content, it is assumed you have Maven installed. In case you don’t, follow this tutorial for a step-by-step guide. To…
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If you’ve ever wondered whether you can upload your own libraries as a dependency using Maven, the answer is yes, you can. And it is really simple. It’s a 2-step process. Step 1 Navigate to your Maven project path in the command line and to upload a library, that’s the structure of the maven command:…
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What is software testing and why is it useful? Testing software in the simplest terms is to evaluate whether it meets all the requirements or not and to also inspect if there are any misbehaviors and bugs associated with its currents state. Testing in Java Java has multiple testing frameworks available, however, in this tutorial,…
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This tutorial will cover how to run Unit tests using the Maven’s Surefire plugin. If you are not familiar with Unit Testing, you can follow this tutorial for a quick catch-up. In our Maven Project, we need the following mandatory dependencies: <dependencies> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-api</artifactId> <version>5.4.2</version> <scope>test</scope> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-engine</artifactId> <version>5.4.2</version> <scope>test</scope> </dependency> </dependencies>…
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What you will need. IDE or a text editor JDK 1.8 or above Maven What exactly is Maven’s multi-module? This multi-module project is built off of a POM aggregator that handles multiple submodules. Often the aggregator is located in the project’s root directory and must have packaging of type pom. The submodules are Maven projects…
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We do not normally need additional dependencies when it comes to creating an executable jar. All we need to do is create a Maven Java project and have a minimum of 1 class alongside the main method. Please note that we assume you have Maven installed on your machine. In case you don’t, follow this tutorial…
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Before proceeding with the next steps, make sure you have JDK and Maven installed on your system. If you don’t have JDK installed, click here. If you don’t have Maven installed, click here. 1. Generating a WAR file using Eclipse Step 1 – Open Eclipse and create a new Maven project (File->New->Other->Maven Project) Step 2…
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Memory can be described as an array of bytes where you can access each byte individually. In each byte or rather, location, in the memory, there is data that you can access, just like in arrays in Java. In 32-bit architectures, each memory “slot” contains 32 bits, or also called 1 word, or just 4…
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In this post, I’ll teach you multiple methods for capturing java heap dump. Critical for memory consumption optimisation, a heap dump is described as a memory print of the Java process.
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This article discusses about Java Garbage Collection (GC) which is considered as one of the complex topics in Java programming language.
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Let’s give an example first before going deeper into what Mutex is: Think of a queue. Doesn’t matter short or long. Now think of a truck that is selling tickets for an amusement park. One person at a time can buy a ticket. When the person has bought the ticket, it is time for the…
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Semaphore can be used to limit the amount of concurrent threads and essentially, this class maintains a set of permits. acquire() takes a permit from the semaphore and release() returns the permit back to the semaphore. In the event of absence of permits, acuire() will block until one is available Semaphore is used to control…
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Stream API allows developers to take advatange of multi core architectures and improve the performance of Java program by creating parallel streams and making your program perform operations faster. There are two ways of creating a parallel stream: by using the parallelStream() method by using the parallel() method When you are using parallel streams, effectively…
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This article talks about the importance of thread synchronization in Java and how you can implement it in your programs.
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Active threads consume system resources, which can cause JVM creating too many threads which means that the system will quickly run out of memory. That’s the problem Thread Pool in Java helps solving. How Thread Pools work? Thread Pool reuses previously created threads for current tasks. That solves the problem of the need of too…
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ThreadLocal is a class that provides thread local variable and is used to achieve thread safety. The data stored will be accessible only by a specific thread. ThreadLocal extends Object class and provides thread restriction which is a “part” from local variable. Creating a ThreadLocal variable ThreadLocal threadLocalExample = new ThreadLocal(); The instantiation of the…
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The following article talks about the livelock and deadlock states in java, how they occur and what can be done to avoid them.
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The result of an asynchronous computation is called Future and more specifically, it has this name because it (the result) will be completed at a later point of time in the future. Future object is created when an asynchronous task has been created. There are many methods that are provided that help to retrieve the result (using get methods(which is…
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Java equals() method and the “==” operator are both used to compare objects for equality. However, they are doing the checking in a very different way, generating different results. The main difference between them is that “==” checks if both objects point to the same memory location and equals() evaluates to the comparison of the…
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Java 8 introduced Lambda Expressions and is one of the biggest, if not the biggest, feature that was introduced because Lambda expression makes functional programming possible and it makes your code way cleaner and overall simplifies the whole code implementation drastically. For example, when you have to work with anonymous class and that class is…
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Java 8 introduced Optional class which is used to manipulate data based on whether a value is present or absent. You can have the same functionality without using this class, however you would end up with way messier code. In other words, you will have less null checks and no NullPointerException’s. Let me give you…
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Java 11 introduced the HTTP Client which can be used to send requests over the network and retrieves their responses. HTTP Client replaces the HttpUrlConnection class as it is considered old and doesn’t support ease of use. HTTP Client API supports both HTTP/1.1 and HTTP/2. HttpClient is also immutable, meaning it can be used to…
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Enum type is a special data type which holds different constants such as WHITE, BLACK, RED. The convention is that they should be named with upper case because, again, they are constants. In java, you define enum type by using the enum keyword. public enum Macronutrients { FATS, CARBOHYDRATES, PROTEIN } If you know all the…
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The super class in Java java.lang.Object provides two important methods for comparing objects: equals() and hashcode(). These methods are widely used when faced against implementing an interaction between classes. In this tutorial, we are only going to look at hashCode(). Method Definition and Implementation hashCode(): By default, this method returns a random integer that is unique every time. If you execute…
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What are unit tests? Unit tests are a method of software testing in which small components of a Java application are being tested. Its purpose is to confirm the fact that every piece of the software behaves as expected. And even if it is, you can use unit testing to determine whether another implementation would…
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This tutorial explains how to display text and graphics on JFrmae for example, lines, circle and rectangle.
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This tutorial explains how you can interact with JFrame by using buttons, listeners and text fields.
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This tutorial will explain how to create Java JAR file with Maven with step by step guidelines and screen shots.
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The “Collections” framework in Java came into action with the release of JDK 1.2 and was expanded quite a few times in Java 1.4 and Java 5 and then again in Java 6.
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Java offers you a variety of collection implementations to choose from. In general you will always look for the collection with the best performance for your programming task, which in most cases is ArrayList, HashSet or HashMap. But be aware, if you need some special features like sorting or ordering you may need to go for a special…
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Java ArrayList class is a resizable array that implements the List interface. It permits all elements, including null and also implements all optional list operations. Most operations that can be run on ArrayList such as size, isEmpty, get, set, iterator and listIterator are all constant time. However, the add operation’s complexity is O(n) time. Compared to LinkedList, the…
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LinkedList class in Java uses a doubly linked list to store elements and it also provides a linked-list data structure. It implements List, just like ArrayList class, and Deque interfaces. Just like arrays, Linked List is a linear data structure but unlike arrays, the elements in the linked list are linked together using pointers. There…
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Collections that use a hash table for storage are usually created by the Java HashSet class. As the name suggests, HashSet implements the Set interface and it also uses a hash table which is a HashMap instance. The order of the elements in HashSet is random. The null element is permitted by this class. In…
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Java TreeSet class is a NavigableSet implementation that is based on TreeMap. The elements are either ordered by a Comparator or simply by their natural ordering. In terms of complexity, this implementation provides log(n) time cost for all basic operations like add, remove, contains. What is important to know about TreeSet in Java TreeSet implements the…
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LinkedHashSet class in Java differs from HashSet as its implementation maintains a doubly-linked list across all elements. This linked list defines the iteration ordering which is the order in which the elements were inserted into the set. It is called an insertion-order. If an element is re-inserted into the set, the insertion order is not affected by…
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Java EnumSet class implements Set and uses it with enum types. EnumSet (as the name suggests) can contain only enum values and all the values belong to the same enum. In addition, EnumSet does not permit null values which means it throws a NullPointerException in attempt to add null values. It is not thread-safe which means if required,…
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Java 8 finally allows us, the programmers, to create thread-safe ConcurrentHashSet in Java. Before then, it was simply not possible. There were variations that tried to improvise the implementation of the above-mentioned class, one of which would be, using ConcurrentHashMap with a dummy value. However, as you might have guessed, all of the improvisations of…
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Arrays’ items are stored as an ordered collection and we can access them by indices. HashMap class in Java on the other hand, stores items in a group pairs, key/value. They can be accessed by an index of another type. This class does not guarantee that there will be a constant order over time. HashMap provides…
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LinkedHashMap is a combination of hash table and linked list that implement the Map interface with predictable iteration order. The difference between HashMap and LinkedHashMap is that LinkedHashMap maintains a doubly-linked list which allows scanning through all of its entries back and forth. The order is maintained, meaning the order in which keys were inserted…
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TreeMap implements the Map interface and also NavigableMap along with the Abstract Class. The map is sorted according to the natural ordering of its keys or by a Comparator provided a the time of initialization. In terms of time complexity, this implementation provides log(n) cost for the containsKey, get, put and remove operations. It’s important…
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EnumMap class implements the Map class and enables the use of enum type keys. Enum maps are maintained in the natural order of their keys. It is important to note that null keys are not permitted. If attempt has been made for adding a null key, NullPointerException will be thrown. However, even though null keys are not allowed, null values are. Since all…
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WeakHashMap in Java implements the Map interface and represents a hash table that has weak keys. If a key is not in an ordinary use, the entry from the map will be automatically removed. This is what differentiates it from other Map implementations. Null and non-null values are supported and the performance is similar to HashMap class in and…
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IdentityHashMap implements the Map interface and two keys are considered equal when checked as k1==k2 (not by using equals method). This itself violates the Map‘s general contract, which means that IdentityHashMap is clearly not a general-purpose Map implementation. There are only so many cases where this class would be useful. IdentityHashMap permits both null values and the null key, alongside all optional map…
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SortedMap interface extends Map and ensures that all entries are in an ascending key order (hence SortedMap). If you want to have it in a descending order, you will need to override the Compare method in the SortedMap which we will do shortly. TreeMap implements SortedMap and it either orders the keys by their natural…
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Even though Map is implemented by many classes, many of them are not thread-safe or some of them are but not efficient. This is why ConcurrentMap was introduced in Java 1.5. It is thread-safe and efficient. Overridden default implementations: compute replaceAll forEach getOrDefault computerIfAbsent computerIfPresent ConcurrentMap consists of an array of nodes that are represented as table…
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Hashtable implements a hash table (as the name suggests) and maps keys to values (like LinkedHashMap). Hashtable class allows non-null objects to be used as a key or as a value. Just like HashMap, Hashtable has two parameters that affect its performance: initial capacity and load factor. The capacity is the number of buckets in the hash…
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This article explains the differences between ArrayList and LinkedList and in which case we should prefer the one over the other.
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Following examples demonstrate how to initialize a Java HashMap using standard and inline methods.
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In this article I will explain the difference between java HashMap and java TreeMap
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Graphs are usually made from vertices and arcs. Sometimes they are also called nodes (instead of vertices) and edges (instead of arcs). For the sake of this tutorial I will be using nodes and edges as reference. Graphs usually look something like this: In many cases, the nodes and the edges are assigned values to…
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Searching and/or traversing are equally important when it comes to accessing data from a given data structure in Java. Graphs and Trees are an example of data structures which can be searched and/or traversed using different methods. Depth-first-search, DFS in short, starts with an unvisited node and starts selecting an adjacent node until there is…
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Searching or traversing is really important when it comes to accessing data from a given data structure. There are different methods of traversing/searching elements within these data structures such as Graphs and Trees. Breadth-first search is one example of these methods. BFS is an algorithm that traverses tree or graph and it starts from the…
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Before starting to explain the different time complexities, let’s first look at what an actual algorithm is. The formal definition of an algorithm is “a process or set of rules to be followed in calculations or other problem-solving operations, especially by a computer.”. So in other words, an algorithm is a defined path which is…
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Serialized object. What does that mean? Java provides a functionality which represents an object as a sequence of bytes which include the object’s data and also information about the object’s type and the types of data stored in that object. When a serialized object has been written into a file, it can later be deserialized,…
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Reflection (which is a feature in Java) allows executing Java program to examine itself (or another code) and manipulate internal properties of the program such as obtaining names of members and perform something on them, like deleting them or displaying them. By default, every object in Java has getClass() which basically determines the current object’s…
Continue readingThis article discusses the concept of weak references in Java.
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Java 8 introduced a new Date-Time API which purpose is to cover drawbacks of the old date-time API. The previous date-time api was not thread safe and the replacement for the new date-time API is that it does not have any setter methods. Another drawback that is fixed by the new API is the poor…
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Today I will show you the very basics of Regular Expressions and how to use them in Java.
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Sometimes you wish to know how much disk space is left on your hard drive. There are several ways to do that. In this example I will show you how to do this with Apache commons.
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In this example I will show you how to generate the MD5 hex sum for a given string using Java
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The Java memory model specifies how the Java virtual machine works with the computer’s memory (RAM). In this tutorial I will show you how to configure the memory used by Java.
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In this tutorial I will show you how to store and retrieve values from a properties file in Java
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This tutorial demonstrates how to install and configure Java 9 Beta on Eclipse Oxygen
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This example demonstrates how to create immutable lists with the new Java 9 Collections factory methods
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This example demonstrates how to create immutable Set with the new Java 9 Collections factory methods
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This example demonstrates how to create immutable Map with the new Java 9 Collections factory methods
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As we know design pattern are created to solve a specific problem. Singleton solve the problem of creating only one object of one class. Singleton design pattern is one of the most popular design patterns, it restricts any class to have only one object. And that object is used where ever required. There are certain…
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The Observer pattern is a software design pattern in which an object, called the subject, maintains a list of all the other objects that depend on it (the subject). These dependents are called observers. They are automatically notified if the state of the subject (the maintainer of all dependents(observers)) changes. It is usually accomplished by…
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This article talks about the factory design pattern in Java which is one of the popular design patterns used in Java.
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Here we will talk about the Java Builder design pattern, where and how it should be used.
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in this tutorial, we will discuss java comparator and its examples. What is Java Comparator? Java Comparator is an interface for arranging Java objects. Summoned by “java.util.comparator,” Java Comparator analyzes two Java protests in a “compare(Object 01, Object 02)” group. Utilizing configurable strategies, Java Comparator can contrast objects with profit a number based for a…
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The JavaMail API “pp”-independent(platform and protocol) framework which purpose is to help build messaging and mail applications. It is
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In this tutorial, we will discuss the Java volatile Example. What is Java volatile? The Java volatile keyword is utilized to check a Java variable as “being put away in fundamental memory”. All the more decisively that implies, that each read of an unpredictable variable will be perused from the PC’s primary memory, and not…
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In short, Docker is a tool that allows you to build, deploy and run applications easily by the usage of so-called containers. These containers let us package all the essentials such as libraries and dependencies. In addition, the containers run on the host operation system. There are many benefits that come when we use Docker. It…
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In the end of this tutorial, you will have installed the right MySQL products needed to develop applications in Spring. You will need two essential things: MySQL Database and MySQL Server. Follow the steps below. Configuring the MySQL Database Visit https://www.mysql.com/downloads/ and then select Community downloads, like so: On the next page, you will see…
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Before testing the MySQL connection from a Java program, we’ll need to add the MySQL JDBC library to the classpath. We will need to download the mysql-connector-java-*.jar file from the downloads page: Now, depending upon your work environment (e.g. Eclipse or Command line) you will have to do either one: If working with Eclipse IDE,…
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Debugging – the technique one uses most and is inevitable. If only there was a tool that allowed us to make this sometimes-tedious task much easier and not-so-tedious… oh wait. There is. Eclipse allows to start a Java programin in the so-called Debug mode. What it is most useful for is that it allows you…
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