jvm - Duplicated Java runtime options : what is the order of preference?

Question

Considering the following command line

java -Xms128m -Xms256m myapp.jar

Which settings will apply for JVM Minimum memory (Xms option) : 128m or 256m ?

Answer 1

As always, check your local JVM's specific implementation but here is a quick way to check from the command line without having to code.

> java -version; java -Xmx1G -XX:+PrintFlagsFinal -Xmx2G 2>/dev/null | grep MaxHeapSize

java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)
uintx MaxHeapSize         := 2147483648        {product}

So you'll see in this case, the second instance of the argument (2G) is what takes precedence (at least in 1.8) and that has been my experience with most other modern versions as well.