Which deployed jar contains android.os.SystemClock

Question

I am trying to run a simple command line java application on dalvikvm using the these instructions. I am running as root so it is not a permissions issue.

Here is the application code:

import android.os.SystemClock;
/**
 * Command that sends key events to the device, either by their keycode, or by
 * desired character output.
 */
public class MWE {
    public static void main(String[] args) {
        System.out.println(SystemClock.uptimeMillis());
    }
}

When I run this on dalvikvm, I get the following error message:

java.lang.NoClassDefFoundError: android.os.SystemClock
        at MWE.main(MWE.java:8)
        at dalvik.system.NativeStart.main(Native Method)

Here is the command that I run, which works for the normal Hello World version of the above application.

/system/bin/dalvikvm -Xbootclasspath:/system/framework/core.jar -classpath /data/local/tmp/MWE.jar MWE

My current conclusion is that android.os.SystemClock does not live inside core.jar. I have speculatively tried to add framework.jar and framework-res.jar as well, but I get the same error.

1. Which of the jars under /system/framework holds the class android.os.SystemClock?
2. In general, is there a place that has a class-to-jar mapping for deployed jars in Android?

Answer 1

On my device (HTC One M8) android.os.SystemClock is in /system/framework/framework3.jar. I believe framework is separated into multiple jars because of the 65k method limit on classes.dex. android.os.SystemClock may be in a different jar on different android devices.

Steps I used to find where android.os.SystemClock was located:

adb pull /system/framework/<filename>.jar

I then decompiled classes.dex to a jar with DexToJar and viewed the packages inside the jar using JD-GUI (you could just open it as a ZIP file, jd-gui is not necessary and for windows only)