What Is JRE and How Does It Work?
As briefly mentioned above, JRE Java Runtime Environment is defined as the environment that enables you to run a program written in the Java programming language. In other words, JRE is not used to write or compile code, but rather to run code that has already been written. So, how does JRE work? Here is the answer!
How JRE Works Step by Step
- In the first step, the user runs a previously compiled Java application, such as a .class or .jar file. These files run as platform-independent bytecode.
- JRE then loads the Java libraries and other components required by the application, preparing the environment needed for the program to run.
- JRE contains a JVM. JVM, which stands for Java Virtual Machine, loads bytecode files into memory and prepares them for execution.
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- Following all necessary security and integrity checks, the JVM verifies that the code can run correctly and securely.
- The Just-in-Time (JIT) Compiler, which is also part of the JVM, converts bytecode into machine code that the relevant operating system can understand.
- The converted code is executed by the processor, allowing the Java application to run.
- While the program is running, JRE also manages memory by automatically clearing unused objects.
- When the application is closed, JRE stops all resources in use and securely terminates the runtime environment.
The Importance of JRE for Cloud-Based Java Applications
Java Runtime Environment (JRE) serves as the fundamental framework required for cloud-based Java applications to run seamlessly on any server or operating system infrastructure. Therefore, it is essential for those using such applications.
- Operating according to the "Write once, run anywhere." philosophy, JRE functions independently of the platform and can therefore run seamlessly across different operating systems in the cloud, such as Windows, Linux, and macOS.
- With its automatic memory management feature called Garbage Collection, it optimizes the memory consumption of applications in response to increasing or decreasing traffic in cloud environments. This is a highly useful feature for preventing server crashes.
- By including only JRE within container technologies such as Kubernetes or Docker, you can make cloud deployment much lighter and faster.
At this point, you may also be interested in our article titled What Is Kubernetes and What Is It Used For?.
Java Runtime Environment (JRE) can be used in almost any area where applications developed with Java need to be executed. Providing the runtime environment required for end users to use Java-based programs seamlessly, JRE has a wide range of use cases, from desktop software to enterprise systems and from cloud applications to IoT solutions. You can see the most common use cases below.
- Desktop Applications: Enables accounting programs, ERP software, educational applications, and office programs developed with Java to run.
- Enterprise Web Applications: Helps e-commerce platforms, CRM systems, and human resources applications developed on Java infrastructure run seamlessly on servers.
- Cloud-Based Applications: Supports the platform-independent execution of cloud services running on different operating systems.
- Microservices Architectures: Enables microservices developed with Java to run reliably and efficiently in container environments.
- IoT and Embedded Systems: Provides the environment required to run applications on Java-based smart devices, industrial automation systems, and various IoT solutions.
Frequently Asked Questions
What is the main difference between JRE and JDK?
JDK (Java Development Kit) includes the tools used to develop and compile Java applications, while JRE (Java Runtime Environment) only provides the runtime environment required to run compiled Java applications. In short, JDK is used for software development, while JRE is used to run applications.
Can JRE be used on its own to develop Java applications?
No. JRE is designed to run Java applications. Tools included in JDK are required for development processes such as writing code, compiling, and debugging.
Does JRE include a JVM?
Yes. JRE consists of the Java Virtual Machine (JVM), core Java class libraries, and other components required for applications to run. JVM is one of the most important components of JRE and enables the application to run by converting Java bytecode into machine code.
Why is JRE important for cloud-based Java applications?
JRE plays an important role in cloud environments because it enables Java applications to run consistently across different operating systems. It also works with container technologies such as Docker and Kubernetes, helping applications to be deployed quickly and reliably.
Which operating systems can JRE be used on?
JRE can be used on many operating systems that support Java, particularly Windows, Linux, and macOS. Thanks to its platform-independent structure, the same Java application can run on different systems without being recompiled, provided that the appropriate JRE version is available.