Java training in chennai: Introduction to the Java runtime environment

Together, the Java Development Kit (JDK), the Java Virtual Machine (JVM) and the Java Runtime Environment (JRE) form a powerful fragment of Java platform components to develop and execute Java applications. I have already presented the JDK and the JVM. In this quick tutorial, you will learn about the JRE, which is the runtime environment for Java.

In practice, a runtime environment is software developed to run other software. As the runtime environment for Java, the JRE contains the Java class libraries, the Java class loader, and the Java virtual machine. In this system:

• The class loader is responsible for correctly loading the classes and connecting them to the main Java class libraries.

• JVM is responsible for ensuring that Java applications have the necessary resources to run and run well on your device or cloud environment.

• The JRE is primarily a container for these other components and is responsible for orchestrating its activities.

What is a runtime environment?

A software program must be run and, for this, it needs an environment to run. The runtime environment loads class files and ensures that there is access to memory and other system resources to execute them. In the past, most software used the operating system (OS) as its runtime environment. The program worked inside the computer it was on, but it had operating system configurations for accessing resources. Resources in this case would be things like memory and program files and dependencies. Java Runtime Environment has changed all this, at least for Java programs.

The Java runtime environment

We can see the software as a series of layers that are located at the top of the system's hardware. Each layer provides services that will be used (and needed) by the layers above it. Java Runtime Environment is a software layer that runs on a computer's operating system, providing additional services specific to Java.

The JRE softens the diversity of operating systems, ensuring that Java programs can run on virtually any OS without modification. It also provides value-added services. Automatic memory management is one of the JRE's most important services, ensuring that programmers do not need to manually control memory allocation and relocation.

In summary, the JRE is a kind of meta-operating system for Java programs. It is a classic example of abstraction, abstracting the underlying operating system into a consistent platform for running Java applications.

Java and JRE memory

Java memory consists of three components: the heap, the stack and the metapace (formerly called permgen).

• Metaspace is where Java keeps the immutable information of its program, as class definitions.

• Heap space is where Java maintains variable content.

• Stack space is where Java stores execution references and function variables.

Memory management in Java 8

Until Java 8, the metapace was known as permgen. In addition to being a much more legal name, the metaspace is a significant change in the way developers interact with Java's memory space. Previously, use the java -XX: MaxPermSize command to monitor the size of the permgen space. From Java 8 below, Java automatically increases the size of the metaspace to accommodate the meta-needs of your program. Java 8 also introduced a new indicator, MaxMetaspaceSize, which can be used to limit the size of goals.

Heap space configuration

Heap space is the most dynamic part of the Java memory system. You can use the -Xms and -Xmx flags to inform Java of the size of the heap start and the size of the permission for it. Understanding how to adjust these indicators to specific program needs is an important aspect of memory management in Java. Ideally, the pile is sufficient to obtain the most efficient garbage collection. That is, you want to allow enough memory to allow the execution of the program, but you do not want it to be larger than necessary.

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Configuration of the stack space

The stack space is where function calls and variable references are routed. The stack space is the source of the second most notorious error in Java programming: the stack overflow exception (the first is the null pointer exception). The stack overflow exception indicates that you ran out of stack space because a lot of it was reserved. Normally, it receives a stack overflow when a method or method calls one another in a circular fashion, thus dedicating an increasing number of function calls to the stack.

You use the -Xss option to configure the initial size of the stack. The stack grows dynamically according to the needs of the program.

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Monitoring of Java applications

Although application monitoring is a function of JVM, the JRE provides configuration options, which are the baseline necessary for tracking. A variety of tools is available for monitoring Java applications, from the classic ones (such as the top Unix command) to sophisticated remote monitoring solutions, such as Oracle infrastructure monitoring.

Among these options are the creators of visual profiles, such as VisualVM, that allow you to inspect a running JVM. These tools allow you to track access points and memory leaks, as well as see the overall memory consumption in your system.

Conclusion

Java Runtime Environment is the disk program that loads Java applications so that the JVM runs. A JRE is included by default when you download the Java Development Kit, and each JRE includes the main Java class libraries, a Java class loader, and a Java virtual machine. It is useful to understand how JVM, JDK and JRE interact, especially to work in cloud and devops environments. In these environments, the JRE assumes a more important role in monitoring and configuration than in the traditional development of Java applications.

Java training in chennai

Sunday, November 18, 2018

Introduction to the Java runtime environment