How to make Java application memory allocated editable?

Question

I have seen a Java application that allows its users to manually edit the application memory allocated. Here is its screenshot:

Does someone know how I can do a similar thing to my application?

Answer 1

It's not Minecraft which allocates memory for itself. MagicLauncher is a seperate program that calls java with the correct parameters to start minecraft.jar.

To allocate memory for Java, you can use for example java -jar -Xmx512 program.jar to give program.jar 512 megabytes of memory.