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Java – How-Tos and Tutorials

On this page, you find an overview of how-tos and tutorials about Java.

Java Basics + Data Structures

This category covers core Java functionality, such as String processing, object conversion, and random number generation, as well as data structures, such as collections, maps and sets, trees, queues, deques, and stacks.

java main method
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Java main()
Method – With New Features 2024

Discover everything about the main method in Java, the starting point of every Java program. Find out more about the components, invocations, and the latest...
java array length feature image
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Array Length in Java

How to find the length of an array in Java? How do you set the length? How much memory does an array occupy and what is the maximum size?
declare and initialize arrays in java
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How to Initialize Arrays in Java

How to declare and initialize arrays in Java? How to copy and fill them? How to convert lists, sets and streams into arrays?
java random numbers
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Generating Random Numbers in Java

How to generate random numbers in Java? How do Math.random() and methods in Random like nextInt() and nextDouble() work?...
java substring method
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Java substring()
Method

Java's String.substring() method is one of the most used Java methods ever....
java comparator comparable compareto
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Comparator, Comparable, compareTo – Comparing Java Objects

How to compare two objects in Java? What is the difference between Comparator and Comparable? How to create a Comparator with Java 8?
Stack, Queue, Deque - Feature Image
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Stack, Queue, Deque in Java

How do the stack, queue and deque data structures work? Which implementations are available in the JDK? Which one should you use when?

Project Amber – Java Syntax Enhancements

In Project Amber, new Java language features are being developed such as switch expressions, text blocks, records, pattern matching, and sealed classes.

statements before super(...)
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Flexible Constructor Bodies: Java Code in the Constructor

As of Java 22, you can finally execute code in constructors before calling super(...) or this(...). This article shows you how.
string templates java
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String Templates in Java

Learn how String Templates in Java simplify the composition of strings from text, variables and calculated values.
unnamed variables and patterns
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Unnamed Variables and Patterns in Java

Variables & patterns that we have to define but do not need can be designated with '_'. Find out what you need to bear in mind.
switch expressions java
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Java Switch Expression

Switch expressions were released in Java 14. This article shows how the arrow notation and the use as expression with return values allows a much more concise,...
java text blocks
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Java Text Blocks

Text blocks are a notation for multiline strings in Java. Why do we need them? How do we write and format them? Which escape sequences can or must we use?
sealed classes java
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Sealed Classes in Java

Sealed classes and interfaces were the big news in Java 17.What are sealed classes and interfaces? How exactly do they work? And why do we need them?
java records
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Java Records

Records are one of two major new features in Java 16....

Advanced Java Topics

This section covers advanced Java topics such as reflection, concurrency, garbage collection, and the Java memory model.

java foreign function and memory api - ffm api
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Java Foreign Function & Memory API
(FFM API)

Learn how to access libraries of other programming languages from Java using the Foreign Function & Memory API.
stream gatherers
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Stream Gatherers – Write Your Own Stream Operations!

Find out what a stream gatherer is and how you can use it to implement any intermediate stream operations.
structured concurrency java
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Structured Concurrency in Java with StructuredTaskScope

What is Structured Concurrency and why do we need it? How does StructuredTaskScope work? What is the advantage of Structured Concurrency?
scoped values java
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Scoped Values in Java

What is a Scoped Value? How to use ScopedValue? How to inherit Scoped Values? What is the difference between ScopedValue and ThreadLocal?
virtual threads java
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Virtual Threads in Java
(Project Loom)

Virtual threads in Java (Project Loom): What are virtual threads? Why do we need them? How do they work? How to use them?

New Java Features

Every new Java release brings big and small changes:

  • Changes to the language itself (lambdas, the module system, var, improvements from Project Amber, ...),
  • API enhancements and
  • Performance improvements under the hood.

In addition, legacy features are regularly marked as "deprecated", then as "deprecated for removal", and later completely removed from the JDK.

In this series of articles, you will learn everything about the most important changes in each Java release.

java 23 features
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Java 23 Features
(With Examples)

All Java 23 features with examples: primitive type patterns; Markdown in JavaDoc; importing modules; `print()`, `println()` and `readln()` without `System.in`...
java 22 features
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Java 22 Features
(with Examples)

All the new Java 22 features with examples: Unnamed Variables & Patterns, Stream Gatherers, Foreign Function & Memory API, Launch Multi-File Source-Code...
java 21 features
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Java 21 Features
(with Examples)

The new Java 21 features with examples: Virtual Threads, Sequenced Collections, Record Patterns, Pattern Matching for switch; new preview features: String...
how to switch java versions in windows
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How to Change Java Versions in Windows
(Updated for Java 22)

In this article, I'll show you how to install several Java versions simultaneously in Windows and how to switch between them on the command line with short...
java 20 features
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Java 20 Features
(with Examples)

The new Java 20 features with examples: Scoped Values (Incubator), Record Patterns (Second Preview), Pattern Matching for switch (Fourth Preview), Foreign...
java 19 features
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Java 19 Features
(with Examples)

The new Java 19 features with examples: Virtual Threads (Preview), Record Patterns (Preview), Foreign Function & Memory API (Preview) + more.
java 18 features
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Java 18 Features
(with Examples)

The new Java 18 features with examples: UTF-8 encoding by default, @snippet tag in JavaDoc, jwebserver, Internet-address resolution SPI + more…
java 17 features
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Java 17 Features
(with Examples)

All new features of Java 17 with examples: Sealed Classes, InstantSource, HexFormat, context-specific deserialization filters, and more...
java 16 features
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Java 16 Features
(with Examples)

All new features of Java 16 with examples: "Pattern Matching for instanceof", Records, Value-Based Classes, Strong Encapsulation, new Stream methods, jpackage...
java 15 features
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Java 15 Features
(with Examples)

All new features of Java 15 with examples: Text Blocks, ZGC + Shenandoah, new String methods, Biased Locking, Sealed Classes (preview), and more...
java 14 features
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Java 14 Features
(with Examples)

All new features of Java 14: Switch Expressions, Helpful NullPointerExceptions, Previews: Records + Pattern matching for instanceof + more...
java 13 features
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Java 13 Features
(with Examples)

All new features of Java 13 with examples: Switch Expressions (2nd Preview), Text Blocks (Preview), Dynamic CDS Archives + More
java 12 features
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Java 12 Features
(with Examples)

All new features of Java 12: new String and Files methods, Teeing Colletor, Default CDS Archives, G1 optimizations + more.
java 11 features
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Java 11 Features
(with Examples)

All the new features of Java 11: "var" in Lambdas, HttpClient, new String and Files methods, Epsilon GC, Flight Recorder and more.
java 10 features
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Java 10 Features
(with Examples)

All the new features of Java 10: "var", Immutable Collections, Optional.orElseThrow(), Application Class-Data Sharing and more.

Article series "Files in Java"

Files

in Java

What you'll learn
  • How to read and write text and binary files
  • Character encoding and line breaks
  • Constructing relative and absolute file and directory names with File, Path, and Paths
  • How to list all files of a directory, how to search files
  • How to move, rename, copy and delete files
  • Saving complex objects and primitive data types in binary files
  • Writing and reading files with FileChannel and ByteBuffer

Java Performance

This category deals with the performance of Java code, i.e., with which Java means a particular task can be executed most efficiently - possibly depending on the Java version. Not only is it important to know how to optimize code, but also when it is better to leave the optimization to the Java Runtime and the Hotspot Compiler.

java string to int
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How to Convert String to Int in Java – Peculiarities and Pitfalls

In today's article you will learn which methods you have to parse a String to an int in Java, and what you have to consider when using these methods.
java int to string
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How to Convert int to String in Java – The Fastest Way

In this article I will show you the fastest method to convert an int to a String in Java. You will be surprised!