Object Identity String in Java with Objects.toIdentityString()
Learn what an object identity string is in Java, how Objects.toIdentityString() and System.identityHashCode() build it, and what its hash part means.
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Lokesh Gupta
Website: https://howtodoinjava.com
Github: https://github.com/lokeshgupta1981/
Twitter: @HowToDoInJAVA
My Articles:
Java Base64 Encode and Decode a File (Text, Image, Large Files)
Base64 encode and decode a file in Java with examples for text and image files, data URIs, streaming large files with wrap(), MIME and decoding errors.
Initialize HashMap in Java: Capacity, Load Factor, newHashMap
Learn to initialize HashMap in Java with Map.of, newHashMap and streams, and see how initial capacity and load factor decide when the map resizes.
TypeScript Method Override: override Keyword and super Calls
A subclass replaces a parent method by overriding it. Learn the override keyword, noImplicitOverride, super calls and the rules the compiler checks.
Using JAXB XmlAdapter and XmlJavaTypeAdapter with Interfaces
For each interface, we must write a custom XmlAdapter class that handles the conversion between the value in Java Object and XML string.
Difference between Camel Case, Pascal Case, Snake Case and Kebab Case
In any programming language, naming conventions are a very important best practice to follow. Different parts of a program are written in specific cases so they can communicate easily their purpose in the source code. This short article lists some popular casings such as camel case, pascal case, snake case, …
[Solved] JAXB Error: No default constructor found on class
Learn to solve the error “No default constructor found” when unmarshaling an XML to Java object using JAXB @XmlTransient and @XmlJavaTypeAdapter annotations.
orElse vs orElseGet in Java Optional (with Examples)
orElse vs orElseGet in Java explained with examples. Learn why orElse always computes its default, when orElseGet saves work and how to avoid side effects.
TypeScript: Create an Object From an Interface (7 Ways)
An interface cannot be instantiated with new, but any object with the right shape matches it. Learn seven ways to create such objects and when to use each.
TypeScript instanceof: Classes, Arrays, Errors, Interfaces
instanceof checks whether an object was created by a class and narrows its type. Learn how it works, where it fails, and how to check interfaces with in and type guards.
TypeScript Interface vs Class: Differences and When to Use
An interface describes a shape and disappears after compilation; a class describes a shape, holds code and exists at runtime. Compare them feature by feature.
TypeScript Generics: Function, Class and Interface Examples
TypeScript generics let one function, class or interface work with many types while the compiler checks every value. Examples cover constraints, keyof, defaults and const type parameters.
TypeScript Extend Interface: extends, Merging and & Types
Extend a TypeScript interface with extends, combine several parents, merge declarations, and learn when an intersection type (&) is the better fit.
TypeScript Interface: Declare, Implement and Use (Examples)
A TypeScript interface names the shape of an object. Learn to declare one, use optional and readonly properties, implement it in a class, and choose between an interface and a type alias.
Spring Boot REST API for Excel File Download
Learn to write Spring Boot RESTs that help in downloading the Excel files (.xlsx) either stored in the server or generating and then sending it.
Spring Boot MVC Exception Views: Custom Error Pages
Learn to create generic and custom error pages for specific HTTP error codes in a Spring Boot application with configuration examples.
Spring Boot @Import and @ImportResource Examples
By leveraging Spring @Import and @ImportResource annotations, we can create more modular, maintainable, and flexible Spring Boot applications.
Different Ways to Load Property Files in Spring Boot
Spring Boot provides various ways to load property files such as default application.properties, spring profiles, custom property files, environment variables, and system properties.
Creating and Building a Spring Boot Project with Gradle
Learn to create a Spring Boot project with Gradle from scratch, configure the build script, create a Spring Boot application class, and run the application.
Python Filter List with filter(): Syntax and Examples
Filter a Python list with filter() and a lambda. See its syntax and return value, and filter strings, objects, None values and items by another list.
Python: Find Most Frequent Element in a List or Array
Find the most frequent element in a Python list with Counter.most_common(), statistics.mode() and multimode(), pandas and NumPy, including ties.
Python: Remove Duplicates from a List and Keep Order
Remove duplicates from a Python list while keeping order with dict.fromkeys(), a seen set, NumPy np.unique() and pandas, plus dedupe by key and timings.
Python MultiDict Examples: Map One Key to Multiple Values
Use the Python multidict library to map one key to several values. Add, getall, update, popall, CIMultiDict for headers, and defaultdict(list) compared.
Python: Keep Last N Items of a List, Array or String
Keep the last N items in Python with deque(maxlen=n) or slicing [-n:]. Covers lists, NumPy arrays, strings, the n=0 trap, file tails and moving averages.
Calculate Number of Weeks Between Two Dates in Java
Calculate the weeks between two dates in Java with ChronoUnit.WEEKS.between(), get leftover days, round up started weeks and count calendar weeks.
Get the Day Name From a Date in Java (Localized)
Get the day name from a date in Java with getDisplayName() and TextStyle, print it in any language, list all names and parse names back.
Split a Date-Time Range into Equal Intervals in Java
Split a date-time range into equal intervals in Java, cut fixed-length chunks, or split by days, weeks, months and years with half-open ranges and DST.
Java StopWatch: Guava, Apache Commons, Spring and java.time
Java StopWatch examples with Guava Stopwatch, Commons Lang and Spring StopWatch, plus a small testable java.time version that records named laps.
Get Elapsed Time Since Midnight in Java (Seconds, Millis)
Get the elapsed time since midnight in Java in seconds or milliseconds with LocalTime, in any time zone, correct on daylight saving days.
Get the Quarter From a Date in Java, Start and End Dates
Learn to get the quarter from a date in Java with IsoFields, find quarter start and end dates, format Q3 labels and calculate fiscal quarters.
Convert Month Number to Name and Back in Java
Convert month number to name in Java with Month.getDisplayName(), and parse full or short month names back to numbers in any locale.
Java Date Format with Day Period: Pattern B Examples
Java date format with day period using pattern B in DateTimeFormatter (Java 16+). Print in the morning or at night, parse it and set custom ranges.
Java Math.divideExact(): Detect Integer Division Overflow
Learn how Math.divideExact() in Java detects the Integer.MIN_VALUE / -1 overflow, how it handles zero, and how it compares to floorDivExact().
Java Math.abs() vs Math.absExact(): Overflow Explained
Java Math.abs() vs Math.absExact() with examples. Why Math.abs(Integer.MIN_VALUE) is negative, when absExact() throws, and safe alternatives.
Java String Concatenation Performance: + vs StringBuilder
Java string concatenation performance on JDK 25 with JMH results, how + compiles since JEP 280, why += in loops is slow, and concat() vs StringBuilder.
Java Text Block Formatting with Variables and Placeholders
Java text block formatting with variables using formatted(), String.format(), MessageFormat and named placeholders, plus what happened to string templates.
Java Multiline String: Text Blocks and Older Options
Write a Java multiline string with text blocks, control indentation, line breaks and trailing spaces, and see the String.join() options for Java 8 to 14.
Create Online Python Editor using Flask, Docker and K8s
Learn to build an online Python editor (using Flask, Docker, and Kubernetes) that allows users to write and run Python code directly from the browser.
Python List Comprehension: if-else, Nested and Examples
Learn Python list comprehension syntax with examples. Place if and if-else correctly, flatten lists, pair two lists with zip() and build dicts and sets.
OpenAI Fine-Tuning: Workflow, Examples and Availability
In this chatGPT tutorial, explore the entire life cycle of fine-tuning models from preparing training data, creating a fine-tuned model, and using it programmatically.
OpenAI API with Python: Setup and Chat Completions Example
Learn the basics of ChatGPT, the ChatGPT API for Python, and how to use it for creating and performing NLP tasks with examples.
Spring 6 Programmatic Validator: A Comprehensive Guide
Spring 6 Programmatic Validator API allows to add fine-grained validation rules beyond the capabilities of annotations-based declarative approach.
Spring 6 JdbcClient: When and How to Use it?
Since Spring 6.1, JdbcClient provides a unified client API for JDBC query and update operations, offering a more fluent and simplified interaction model.
Big O Notation: Measuring the Algorithm Efficiency
Big O notation categorizes the efficiency of a given algorithm and describes the upper bound of the growth rate of a function as the input grows.
Java Thread Dump: Capture with jcmd, jstack and Analyze It
Capture a Java thread dump with jcmd, jstack, kill -3 or JSON for virtual threads, read every line and find deadlocks, CPU hogs and stuck pools.
Hibernate Soft Delete: @SoftDelete Example and Strategies
Soft delete rows with Hibernate’s @SoftDelete: see the UPDATE that replaces DELETE, choose the DELETED, ACTIVE or TIMESTAMP strategy, read and restore deleted rows with native SQL, and avoid unique constraint errors.
Spring WebClient Retry and RetryWhen (with Examples)
Learn to retry the failed requests with Spring WebClient’s retry() and retryWhen() operators including retry on specific exception cases.
Running JUnit Tests with Gradle
By utilizing the –tests option, we can run unit tests using Gradle from entire test suites to specific test classes or methods.
Non-Static @BeforeAll and @AfterAll in JUnit (PER_CLASS)
Make JUnit @BeforeAll and @AfterAll non-static with @TestInstance(PER_CLASS). Project default, @MethodSource, @Nested, shared state and parallel tests.
Spring Bean Naming: Default, Explicit and Custom Strategies
In Spring, the default naming strategy utilizes the named of annotated classes or methods. Learn to customize it by explicit or custom naming with examples.