Question: I am trying to use some arguments for an Instrumentation test. I noticed that I can read system properties with `System.getProperty()` function. So I use setprop command to set a system property. For example: `adb shell setprop AP 123`.
Inside my Test code I try to read this AP property with : 

```

tmp = System.getProperty("AP"); 
Log.d("MyTest","AP Value = " + tmp);

```

Then I use logcat to view this debug message but I get a null value for this property. Any ideas on what could be wrong? 
Note that I can still read the system property with `adb shell getprop AP` command.

Answer: 
To get the property set by 'setprop', there are two options:  

One. use android.os.SystemProperties, this is a hide API. use it like this:

```
Class clazz = null;
clazz = Class.forName("android.os.SystemProperties");
Method method = clazz.getDeclaredMethod("get", String.class);
String prop = (String)method.invoke(null, "AP");
Log.e("so_test", "my prop is: <" + prop  + ">");

```

Two. use 'getprop' utility:

```
Process proc = Runtime.getRuntime().exec(new String[]{"/system/bin/getprop", "AP"});
BufferedReader reader = new BufferedReader(new InputStreamReader(proc.getInputStream()));
Log.e("so_test", "my prop is: " + reader.readLine());

```

Maybe using functions availble in NDK is an option too, but why bother?
System properties are read once when the root VM (Zygote) is started, which in turn spawns other Dalvik VMs like that of your application. That means you cannot set system properties on the fly.

Try restarting Zygote using `adb shell stop` (wait until it has stopped) and `adb shell start` (wait until it has restarted), then try again. Or simply reboot the device or emulator.