Java programming language: A comprehensive insight into one of the most powerful languages in software development

Published 29. Juni 2023

Introduction to Java

Java is an object-oriented programming language that was developed by Sun Microsystems and is now supported by Oracle Corporation. Java is one of the most commonly used programming languages and is used for the development of applications, web applications, mobile applications and games.

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What is Java?

Java is a platform-independent programming language, which means that Java code can be executed on different operating systems without having to rewrite the code for each operating system. Java code is compiled into bytecode that can be executed on any platform that has a Java Virtual Machine (JVM).

Java programming language	Description
Object-oriented programming language	Java is a strongly object-oriented programming language based on classes and objects.
Platform independence	Java programs can be executed on various platforms and operating systems.
Strict typing	Java is a statically typed language that performs a strict type check at compile time.
Large standard library	Java offers an extensive standard library with many predefined classes and functions.
Robust error handling	Java has mechanisms for robust error handling, such as exception handling.
Multithreading support	Java supports the simultaneous execution of several threads, which enables the development of parallel programs.
Simple memory management	Java automatically takes over memory management through the garbage collector, which saves developers work.
High security	Java offers a secure execution environment with sandbox support and security mechanisms.
Wide range of applications	Java is used in various areas, from desktop and web development to mobile applications and large enterprise systems.
Active developer community and support	Java has a large developer community that provides extensive resources, documentation and support.

Java platforms

Java platforms are software environments that make it possible to run Java applications. The three most important Java platforms are

Java SE (Standard Edition) - for desktop applications and general applications
Java EE (Enterprise Edition) - for enterprise applications
Java ME (Micro Edition) - for mobile applications and embedded systems

Java development environments

Java development environments (IDEs) are software applications that allow developers to write, test and debug Java code. Some of the most popular Java IDEs are:

Eclipse
NetBeans
IntelliJ IDEA

How does the Java Virtual Machine work? (JVM)

Component	Description
Class Loader	Loads Java classes into the JVM and is responsible for class management. There are different types of class loaders, such as the bootstrap class loader, extension class loader and application class loader.
Execution Engine	Executes the Java bytecode and consists of the just-in-time (JIT) compiler and the interpreter. The JIT compiler translates the bytecode into machine-specific code, while the interpreter interprets the bytecode directly.
Garbage Collector	Manages the memory and performs automatic garbage collection by identifying and releasing objects that are no longer used. There are different types of garbage collectors, such as the mark-and-sweep algorithm or the generational garbage collector.
Runtime Data Area	The Runtime Data Area is the memory area used by the JVM during execution. It consists of various sections, such as the Method Area, Heap, Stack, PC Register and Native Method Stack.
Java Native Interface (JNI)	Enables interaction between Java and native code by allowing Java code to call native code and vice versa. This enables the integration of Java with other programming languages and operating system APIs.
Java API Libraries	Contains the extensive collection of Java classes and libraries that can be used in the development of Java applications. These libraries offer a variety of functions to facilitate various tasks, such as working with data structures, network connections, file systems and much more.

The JVM (Java Virtual Machine) is a virtual machine that enables the execution of Java programs. Here is a basic explanation of how the JVM works:

Compilation: Java source code is first translated into so-called "bytecode" using a Java compiler. The bytecode is a platform-independent representation of the source code.
Loading the classes: The JVM loads the required Java classes into the memory. The class loader is responsible for loading and managing the classes. There are different types of class loaders that are responsible for different classes.
Verification: The JVM verifies the loaded bytecode to ensure that it complies with the security guidelines and is correct. This prevents unsafe or incorrect code from being executed.
Execution: The JVM executes the bytecode. There are two main components: the interpreter and the just-in-time (JIT) compiler. The interpreter reads the bytecode line by line and executes the corresponding instructions. In the case of repeatedly executed code sections, the JIT compiler can translate the bytecode into machine-specific code in order to improve the execution speed.
Memory management: The JVM manages the memory for the Java application. This includes the allocation and release of memory for objects and the execution of automatic memory cleanup by the garbage collector. The garbage collector recognizes objects that are no longer referenced and automatically releases the memory.
Exception handling: The JVM handles exceptions that may occur during execution. It enables exceptions to be caught and handled by the corresponding exception handling mechanisms in Java.
Java Native Interface (JNI): The JVM enables interaction between Java code and native code through the Java Native Interface (JNI). This enables native functions to be called and Java to be integrated with other programming languages.

The JVM also offers other functions such as thread management, security, JIT optimizations and more. By combining all these components, the JVM enables platform independence and the efficient execution of Java programs on different operating systems and hardware architectures.

Java basics

Before you can start developing Java applications, you need to understand the basics of Java syntax, data types, variables and control structures.

Java syntax

Java -syntax is the grammar of the Java programming language. Java code is organized in classes that contain methods, which in turn contain statements. Java code is written in curly brackets and statements are separated by semicolons.

Data types

Java has eight primitive data types:

byte
short
int
long
float
double
char
boolean

Java also has reference data types that are defined by classes.

Variables and constants

Java variables are memory areas that can store values. Java constants are variables that cannot be changed. Constants are declared with the keyword "final".

Operatoren

Java operators are used to manipulate values. Java has arithmetic, assignment, comparison, logical and bitwise operators.

Control structures

Java control structures are used to control the flow of Java code. Java has conditional statements (if-else), loops (for, while, do-while) and switch statements.

Object-oriented programming in Java

Object-oriented programming (OOP) is a programming paradigm based on the use of objects. Java is an object-oriented programming language and supports the OOP principles.

Classes and objects

Java classes are blueprints for objects. Classes define the properties (variables) and behavior (methods) of objects. Objects are instances of classes.

Inheritance

Inheritance is an OOP principle that makes it possible to transfer properties and behavior from one class to another. The class that inherits the properties and behavior is called a subclass, while the class from which the properties and behavior are inherited is called a superclass.

Polymorphism

Polymorphism is an OOP principle that allows objects to take on different forms. Polymorphism is achieved through inheritance and interfaces.

Abstract classes and interfaces

Abstract classes and interfaces are OOP concepts that make it possible to define abstract methods that must be implemented by subclasses. Abstract classes cannot be instantiated, while interfaces only contain abstract methods.

Java APIs

Java APIs (Application Programming Interfaces) are collections of classes and interfaces that can be used by Java developers to implement certain functions in their applications.

Java Collections Framework

The Java Collections Framework is a collection of classes and interfaces that can be used to store and manage data in Java applications. The framework contains classes such as ArrayList, LinkedList, HashSet and TreeMap.

Java IO

Java IO (Input/Output) is a collection of classes and interfaces that can be used to read and write data from files, networks and other sources.

Java Networking

Java Networking is a collection of classes and interfaces that can be used to create and manage network connections in Java applications.

Java Concurrency

Java Concurrency is a collection of classes and interfaces that can be used to write parallel and concurrent programs in Java.

Java tools and frameworks

Java tools and frameworks are software applications and libraries that can be used by Java developers to simplify the development of Java applications.

JUnit

JUnit is a framework for Java -unit tests. It enables developers to write and execute tests for individual methods and classes.

Maven

Maven is a build management tool for Java applications. It enables developers to manage dependencies, automate builds and deploy applications.

Spring Framework

The Spring Framework is a framework for the development of Java applications. It provides support for the creation of web applications, database applications and other types of applications.

Hibernate

Hibernate is a framework for object-relational mapping (ORM) in Java applications. It enables developers to store and retrieve objects in database tables.

Advanced Java topics

Advanced Java topics are topics that go beyond the basics of Java and are relevant for advanced Java developers.

Generics

Generics are a Java feature that makes it possible to ensure type safety in Java applications. Generics enable developers to write classes and methods that can work with different data types.

Annotationen

Annotations are a Java feature that makes it possible to integrate metadata into Java code. Annotations can be used to provide information about classes, methods and variables.

Reflection

Reflection is a Java feature that makes it possible to retrieve information about classes and objects at runtime. Reflection can be used to dynamically load classes, call methods and change variables.

Java 8 Features

Java 8 is a version of Java that was released in 2014. Java 8 contains new features such as lambda expressions, streams and the new file and time API.

Strengths and weaknesses

Java also has strengths and weaknesses. The table below illustrates this:

Strengths	Weaknesses
Platform independence	Complexity
Large developer community	Slower execution speed compared to other languages
Mature and stable language	Higher memory requirements compared to linguistic alternatives
Extensive libraries and frameworks	Outdated syntax compared to more modern programming languages
Object-oriented programming	Management of the memory area by garbage collector can lead to unpredictable performance problems
Simple integration of external libraries	Longer learning curve for beginners
High security thanks to special features such as bytecode verification	Difficult handling of concurrency and parallel programming
Good support for multithreading	Restrictions in hardware-related programming
Good support for enterprise applications	Limited possibilities for low-level manipulations

Here are some weaknesses that are often associated with the Java programming language:

Higher resource consumption: Java applications can have a higher resource consumption compared to some other languages, which can affect efficiency and scalability.

Strict syntax and conventions: The strict syntax and conventions of Java can mean that developers need longer development times, especially for complex projects.
Complexity of advanced concepts: Some advanced concepts in Java, such as multithreading, can be complex for beginners and require a deeper understanding in order to use them effectively.
Longer start times: Java applications often have longer start times compared to applications developed in other languages. This can be particularly problematic for applications with short execution times.
Limited support for low-level programming: Java is located at a higher level of abstraction and therefore offers a higher level of abstraction compared to languages such as C++ or Rust offer limited support for low-level programming and hardware-related operations.
Tighter integration with native operating system APIs: The tight integration of Java with native operating system APIs can lead to increased complexity, especially if platform-specific functions are to be used.
Java is much more complicated than languages like Python , JavaScipt and PHP.
Java is often C# equal.

It is important to note that these weaknesses of Java are relative and do not mean that Java is a bad programming language overall. Java has many strengths and is used successfully in a variety of application areas. The choice of programming language depends on the specific requirements of the project and the preferences of the developers.