How can I access Virtual Machine Arguments in Java Applications?

Accessing Virtual Machine Arguments in Java Applications

When working with Java applications, it becomes necessary to access virtual machine (VM) arguments to control various aspects of the application's behavior. One common scenario is the need to check if a specific VM option is explicitly set or has its default value.

To address this need, several classes and methods are available in the Java API. However, classes like java.lang.System and java.lang.Runtime do not provide direct access to VM arguments.

To obtain VM arguments from within a Java application, consider the following approach:

Using System Properties

The most convenient method for accessing VM arguments is through system properties. You can pass the desired argument to the JVM at startup using the -D option, as follows:

java -Dname=value [Main Class] [Arguments]

Within your Java code, you can retrieve the specified value using the System.getProperty(String key) method:

String value = System.getProperty("name");

This approach allows you to check if a VM argument is explicitly set by examining the existence of the corresponding system property. If the property is present, the argument has been set, while its absence indicates that the default value was retained.

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