What is the difference between Java System Properties and Environment Variables?

Java System Properties vs Environment Variables

In Java, the distinction between system properties and environment variables becomes crucial for managing system configurations.

System Properties (System.getProperties())

System properties represent settings that are passed to the Java Virtual Machine (JVM) through the command line using the -Dpropertyname=value syntax. They can also be modified programmatically at runtime using the System.setProperty(String key, String value) method or by loading a property file into System.getProperties(). To retrieve system property values, either System.getProperty(String key) or System.getProperty(String key, String def) can be employed.

Environment Variables (System.getenv())

Environment variables, on the other hand, are set within the operating system and reside outside the Java environment. In Linux, they are set using the export command and on Windows using SET. Unlike system properties, environment variables cannot be dynamically modified within the Java program itself. To access environment variables in Java, the System.getenv(String name) method is utilized.

In summary, system properties provide a flexible and convenient mechanism for runtime configuration, while environment variables reflect system-level settings that cannot be altered by the Java program. Understanding this distinction is essential for managing the runtime environment and ensuring the expected operation of Java applications.

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