What\'s the Difference Between System Properties and Environment Variables in a JVM?

Understanding System Properties and Environment Variables in a JVM

In the realm of Java Virtual Machine (JVM), system properties and environment variables play crucial roles in configuring and customizing the runtime environment. While both provide a means to store key-value pairs, there are distinct differences between the two.

System Properties

System properties are set during JVM startup using the -D flag. They allow you to customize the JVM's behavior and can be added or modified at runtime using the System.setProperty() method. These properties are stored in the System.getProperties() object.

Environment Variables

Environment variables, on the other hand, are defined in the operating system (OS). Unlike system properties, they are external to the JVM and must be set in the OS environment. Environment variables cannot be modified at runtime using Java code.

Usage and Access

To access system properties, use System.getProperty() or System.getProperty(String key, String def) to retrieve a specific property or its default value.

To access environment variables, use System.getenv(). This method requires a string parameter specifying the environment variable name.

Scope and Inheritance

System properties are inherited by child JVMs. This means that if you set a system property in a parent JVM, it will be available in any child JVMs that it launches. Environment variables, however, are not inherited across JVMs.

Source of Configuration

System properties are typically used for JVM-specific configurations, while environment variables are used for OS-level settings that may be shared across multiple applications on the same system.

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