1. Change the value of app_name
1.1 Open the file in the res/strings.xml
1.2 Inside of the tag <string name="app_name"> change "oldName" to "newName"
This will change the name showed as title of the application. If you want to a cleaner change, continue. Otherwise, it should be enough to change the name of the application for the users
Optional: Change also the tag <resources> <string name="hello">. It will affect the demo showed at beginning.
2. Change the name in the AndroidManifest.xml
2.1 Open the AndroidManifest.xml
2.2 Find the xml tag called: activity with an action called android.intent.action.MAIN. More or less like this:
<activity android:name=".oldName" android:label="@string/app_name">
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
2.3 Modify the tag "android:name" from ".oldName" to ".newName".
3. Change the name of the java file
3.1 Right click on the java file OldName.java and choose Refactor -> Rename
3.2 Change "OldName" by "NewName" and press "Finish"
If you want to know how to change also the name of the package, see this post: