how to correctly execute su from Android application

This way:
Runtime.getRuntime().exec(new String[]{"/system/bin/su", "-c", "setprop ctl.stop zygote"});
If you are getting failures like this:
W/su ( 1043): request rejected (0:0->0:0 /system/bin/setprop)
that means that

• you didn't send "-c", or
• you didn't give it a parameter, or
  
• you gave it more than one parameter

You have to make sure that after "-c" you only send one parameter. Alternate syntax would be this:
Runtime.getRuntime().exec("/system/bin/su -c 'setprop ctl.stop zygote'");

Starting and stopping Android core services from command line

Imagine, for example, that you need to stop the Zygote service and start it again later, because you're toying with Android internals and Zygote is getting in the way.
Or maybe you want to test out a new bootanimation binary, and for some reason running /system/bin/bootanimation directly is not what you want.
This is what you do instead:
setprop ctl.stop zygote
setprop ctl.start bootanim
Simple, right? Then how come it's ungooglable?

You can do all this from Java too, just use System.setProperty(). See this article for more detailed info about properties.

you gotta be effin kidding me

While trying to solve this issue, i have found a document from RIM's Knowledge Base about verification errors in Java packages.
This is it.
Some choice tidbits:

7. Comment out any non-executable code. Verification errors might be related to the size of the main code file and the library files. If you comment out non-executable code, the file sizes change, which may correct the problem.

2. Remove any System.out.* calls. These generally do nothing on the BlackBerry smartphone, but they might cause verification errors.
3. Remove unused import statements.

I have nothing. My mind is blown. How can anyone ever develop anything for this device?