OpenJDK中的JVM参数列表中的“：=”表示什么？

Question

I wanted to see all the JVM arguments available in openjdk 1.8, and executed the following command:

java -XX:+PrintFlagsFinal -version

It outputted all the available arguments in JVM, and I observed that a few flags are having the following format:

uintx MaxHeapSize   := 9449766912  {product} 

bool UseParallelGC  := true        {product}

In the above flags, what does the ":=" indicate?

Answer 1

:= denotes that the flag value was overriden either by JVM ergonomics or manually via a command line option.

Here is the source of the function that prints flags.

Answer 2

The := indicates it is the current value.

If you haven't changed it then this is the default value.

I often use this option with grep to find what I want.