Question
What happens when duplicate Java runtime options are specified in the command line, specifically for -Xms memory settings?
java -Xms128m -Xms256m myapp.jar
Answer
When duplicate Java runtime options are provided in the command line, the Java Virtual Machine (JVM) ignores the earlier settings in favor of the last one specified. This can lead to confusion, especially when configuring memory parameters like the initial heap size (-Xms).
java -Xms256m myapp.jar // Use this instead of multiple -Xms options.
Causes
- Multiple specifications of the same option on the command line.
- Misunderstanding the precedence of command line arguments.
Solutions
- Always specify Java runtime options only once to avoid ambiguity.
- Use scripts or configuration files to manage JVM arguments in a clearer way.
Common Mistakes
Mistake: Using multiple -Xms options without understanding their precedence.
Solution: Only specify -Xms once with the desired value to avoid confusion.
Mistake: Assuming that earlier options take precedence over later ones.
Solution: Remember that the last specified option will be the one that the JVM uses.
Helpers
- Java runtime options
- -Xms option precedence
- JVM memory settings
- Java command line parameters
- Java heap size configuration
