JRE - платформа для запуска Java-приложений

JRE (Java Runtime Environment)

JRE (Java Runtime Environment) is a software required for executing programs written in the Java language. It includes the Java Virtual Machine (JVM) and other components such as class libraries and executable files necessary for running and operating the program.

The main component of JRE is the Java Virtual Machine (JVM). JVM serves as the foundation for executing Java programs. It interprets and executes Java bytecode, which is an intermediate representation of the Java program. JVM interprets and executes the bytecode in real-time, ensuring Java's cross-platform compatibility. Thanks to JVM, Java programs can be run on any platform where the corresponding version of JRE is installed.

In addition to the virtual machine, JRE also includes class libraries that provide a set of ready-made functions and methods for Java application development. These class libraries contain implementations of standard classes and interfaces, such as collections, input-output, network interaction, and more. Thanks to these class libraries, developers can utilize ready-made functionality without the need to rewrite it.

An example of using JRE can be as follows:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

In this example, we create a simple Java program that prints the string "Hello, World!" to the console. To run this program, we need to install JRE on our computer. After installing JRE, we can execute the program from the command line or from development environments such as Eclipse or IntelliJ IDEA.

Furthermore, JRE enables the execution of Java programs in web browsers. Previously, Java applets were a popular way to add interactivity to web pages. With the help of JRE, browsers could execute Java applets without the need for a full Java Development Kit (JDK) installation.

In recent years, the usage of Java applets in web applications has significantly declined, and most browsers have discontinued their support. Instead, Java developers prefer to use other technologies such as JavaFX or web services to create more modern web applications.

Thus, JRE plays an important role in executing Java programs. It includes the Java Virtual Machine and class libraries that allow Java programs to be cross-platform and utilize ready-made functionality. JRE also enables the execution of Java applications in web browsers, although this capability has become less popular in recent years.