How can I call an external application from my application?
E.g: I need to call Shazam (application) from my app.
I can see the package name of the application in the logcat.
will that be useful for any purpose?
You can call a third party application's activity in the following way.
final Intent shazamIntent = new Intent("com.shazam.android");
shazamIntent .setComponent(new ComponentName("com.shazam.android","com.shazam.android.Splash"));
startActivity(shazamIntent );
But, this is not a great way to go about it. In case the package name changes (which is a very remote possibility) or the activity name changes (Splash could change to something else) your application would break.
If Shazam has an Intent which can be invoked to start listening to a song use that (not sure if they have one).
Also, do necessary check in case Shazam is not installed so that your call doesn't crash.