Чашечка Java

How to convert a Map to List in Java? HashMap to ArrayList Example Before converting a Map to a List in Java,  we should be very clear about these data structures which are widely used in Java. So let's begin with Map. What is Map? Map is an Interface in Java which store key and value object. It's a Java representation of a popular hash table data structure that allows you to search an existing element in O(1) time, at the same time also makes insertion and removal easier.  We use a key object to retrieve the value object by using hashing functionality provided by Map. As we have seen in how the get method of HashMap works, In Java, the equals() and hashcode() methods are an integral part of storing and retrieving objects from it. The map allows duplicate values but no duplicate keys. Java Interview questions and tutorials Read: http://www.java67.com/2015/01/how-to-convert-map-to-list-in-java.html

How to use Lambda Expression and method reference in Java? Example Tutorial Hello guys, if you are wondering what is lambda expression and method reference in Java then you are at the right place. Earlier, I have shared 10 Stream API examples and in this article, I will share everything I know about Lambda expression with you. The Lambda expressionis one of the most important features of Java 8 which has opened a whole new dimension of programming paradigm in Java. It is the feature which made the Functional Programming possible in Java because now you can pass the code to a function to execute as opposed to an object. You might be a bit surprised but if you look from a developer's point of view, it is nothing but a way to pass your code to a method in Java. Java Interview questions and tutorials Read: http://www.java67.com/2017/06/10-points-about-lambda-expressions-in-java-8.html

Что означает I в ACID и как это можно использовать Пройдя много собеседований, выяснилось, что довольно приличная часть собеседующих, спрашивавших или как-то затрагивавших тему транзакций и их работы, не знают как работают транзакции и что означает для разработчика термин изоляция. Вплоть до архитектора в одной очень большой российской компании, для которого выводы, использованные мною для формулирования решения при прохождении архитектурной секции оказались чем-то вроде бреда. Пока готовится вторая статья (Миллиард абитуриентов МИРЭА 2), можно отвлечься и разбрать тему, продемонстрировать разработчикам что означает для них I в ACID. Попробовать заблокировать запись Читать: https://habr.com/ru/post/684570/?utm_campaign=684570

Difference between HashMap vs TreeMap vs LinkedHashMap in Java Hello guys, if you are wondering when to use HashMap, TreeMap and LinkedHashMap in Java and want to understand difference between them then you are at the right place. Earlier, I have shared difference between HashSet, TreeSet, and LinkedHashSet and in this article, I will explain the difference between these three common Map implementation HashMsp, TreeMap, and LinkedHashMap. Though all three classes like HashMap, LinkedHashMap and TreeMap are implementation of java.util.Map interface, there is some functional difference between them. Perhaps most notable difference between them comes from their iteration order. HashMap makes absolute no guarantee about in which order you can iterate their keys, any application depending upon iteration order of HashMap is fragile, because it can change anytime. In fact, in Java 7, iteration order of HashMap is different than Java 6. Java Interview questions and tutorials Read: http://www.java67.com/2022/05/hashmap-vs-treemap-vs-linkedhashmap-in.html

3 Examples to Convert Date to LocalDate in Java 8? Tutorial One of the great features of Java 8 is the new Date and Time API which is intended to fix existing issues related to mutability and thread-safety with existing java.util.Date class. But given java.util.Date is used very heavily across all the Java applications, you will often end up with a situation where you need to convert java.uti.Date to java.time.LocalDate while working in Java 8. Unfortunately there is no toLocalDate() method in the java.util.Date class. Though, you can easily convert Date to LocalDate if you are familiar with how new and old API classes map to each other. Java Interview questions and tutorials Read: http://www.java67.com/2019/10/3-ways-to-convert-javautildate-to-LocalDate-java8-example.html

Composite Design Pattern Example in Java and Object Oriented Programming Hello guys, if you are wondering how to use Composite design pattern in Java then you are at the right place. Composite design pattern is another object oriented design pattern introduced by Gang of Four in there timeless classic book Design pattern : Elements of Reusable software. Composite pattern as name suggest is used to compose similar things together, like similar objects. It implements an interface and also contains other objects which implements the same interface, also known as containee. One of the best example of Composite pattern from Java standard library is Swing's container classes e.g. Panel, which not only are Components by themselves, but also contains other components like JButton, Label, JTable etc. Java Interview questions and tutorials Read: http://www.java67.com/2022/08/composite-design-pattern-example-in.html

6 Advanced Comparator and Comparable Examples in Java 8 The JDK 8 release has completely changed the way you compare objects and sort them in Java. The new features of the Java 8 language e.g. lambda expression and method reference have made it easier to implement both Comparator and Comparable interface, as you don't need an Anonymous class for inline implementation. Now, you can create Comparators in just one line by using lambdas and method reference as we'll see in this article. Other features like providing default and static methods on interfaces have also made a huge difference when it comes to Comparator. They helped Java API designers to redesign and evolve existing interfaces, which wasn't possible earlier without breaking existing clients of those interfaces. Java Interview questions and tutorials Read: http://www.java67.com/2019/06/top-5-sorting-examples-of-comparator-and-comparable-in-java.html

Технологии NiFi & Kafka: применение (часть 2) Добрый день, меня зовут Рустам Ахметов, я архитектор ГК Юзтех и интеграционной шины данных UseBus. В предыдущей статье я рассказывал о Kafka и её аналогах, а сегодня хочу рассмотреть NiFi. Вы узнаете: Читать: https://habr.com/ru/post/684312/?utm_campaign=684312

JSON Web Token (JWT) — пример Java реализации на Spring Boot OAuth2 Resource Server 6.0 Доброе время! Часть 2-я по открытому занятию нового учебного курса: реализация простого JWT через новый Spring Boot OAuth2 Resource Server (первая часть: Spring Boot 3.0 — готовимся заранее). Что такое JWT и зачем, писать здесь не буду - в сети материалов много, начинать знакомство обычно рекомендую с Википедии. А вот хорошая ссылка по реализации JWT+OAuth2. Здесь я привожу Java код, основанный на официальном примере spring-projects - простейшей реализации JWT Login Sample (без refresh token и отдельного авторизационного сервера), "творчески доработанный" и с моими пояснениями. Еще раз - без теории, для тех, кому интересен код актуальной Java реализации. Если это Вы - прошу к прочтению. Читать: https://habr.com/ru/post/684270/?utm_campaign=684270

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How to convert String to long in Java? Example You can parse a String literal containing valid long value into a long primitive type using parseLong() and valueOf() method of java.lang.Long class of JDK. Though there is a couple of difference between valueOf() and parseLong() method e.g. valueOf() method return a Long object while parseLong() method return a Long object, but given we have autoboxing in Java, both method can use for parsing String to create long values. In the last article, you have learned how to convert a Long value to a String in Java,and in this tutorial, you will learn the opposite, i.e. how to parse a String to a long value in Java. Java Interview questions and tutorials Read: http://www.java67.com/2015/07/how-to-parse-string-to-long-in-java.html

How to convert String to Double in Java and double to String with Example There are three ways to convert a String to double value in Java, Double.parseDouble() method, Double.valueOf() method and by using new Double() constructor and then storing the resulting object into a primitive double field, autoboxing in Java will convert a Double object to the double primitive in no time. Out of all these methods, the core method is parseDouble() which is specially designed to parse a String containing floating-point value into the Double object. Rest of the methods like valueOf() and constructor uses parseDouble() internally. This method will throw NullPointerException if the string you are passing is null and NumberFormatException if String is not containing a valid double value e.g. containing alphabetic characters. Java Interview questions and tutorials Read: http://www.java67.com/2015/06/how-to-convert-string-to-double-java-example.html

How to check if two String variables are same in Java? equals(), equalsIgnoreCase() and == operator Example There are multiple ways to compare two strings alphabetically in Java e.g. == operator, equals() method or compareTo() method, but which one is the best way to check if two strings are equal or not? Programmers often confused between == operator and equals() method, and think that comparing strings using == operator should be faster than equals() method, and end up using that. Though they are not completely wrong, they often missed the point that == operator is designed to compare object equality,not String equality, which is actually defined in equals()method and compare Strings alphabetically. Java Interview questions and tutorials Read: http://www.java67.com/2013/08/best-way-to-compare-two-strings-in-java.html

Processing Data with Kotlin Dataframe Preview Kotlin DataFrame, available as a first public preview, is a new library for processing data from any source, such as CSV, JSON, Excel and Apache Arrow files. The DataFrame works together with Kotlin data classes and hierarchical data schemas by using a Domain Specific Language (DSL). By Johan Janssen Read: https://www.infoq.com/news/2022/08/kotlin-dataframe-preview/

Why Java Does Not Support Destructor? Read: https://www.thejavaprogrammer.com/why-java-does-not-support-destructor/

Spring Boot 3.0 — готовимся заранее Здравствуй, читатель Хабра! До выхода Spring Boot 3 осталось совсем немного - 3 месяца. Уже появляются статьи - What’s New, It's time to get ready. Недавно JetBrains выпустила IDEA с поддержка Spring 6 и Spring Boot 3. Самое время потренироваться заранее в миграции. В разработке нового учебного курса я попробовал перевести свой открытый учебный проект Spring Boot 2.x + HATEOAS на Spring Boot 3, шаги и код проекта ниже. Читать: https://habr.com/ru/post/683936/?utm_campaign=683936

Java News Roundup: JDK 19-RC1, Multiple Spring Updates, Micronaut, Helidon, Payara This week's Java roundup for August 15th, 2022, features news from JDK 19, JDK 20, Spring Boot versions 2.7.3 and 2.6.11, Spring Authorization Server versions 1.0.0-M1 and 0.4.0-M1, Spring Security versions 5.7.3 and 5.6.7 and 5.8.0-M2, Spring Cloud Dataflow 2.9.5, Spring Shell 2.1.1, Payara Platform 5 Community Edition, Micronaut 3.6.1, Helidon 3.0.1 and Apache Camel 3.14.5. By Michael Redlich Read: https://www.infoq.com/news/2022/08/java-news-roundup-aug15-2022/

Spring Authorization Server 1.0 Planned for November 2022 Spring Authorization Server 1.0 is planned for a GA release in November 2022, after starting the project two years ago. The Spring Authorization Server project replaces the, already End of Life, Spring Security OAuth project. The project is led by the Spring Security team and delivers support for OAuth 2.1 Authorization Server for Spring applications. By Johan Janssen Read: https://www.infoq.com/news/2022/08/spring-authorization-server-1-0/