A class implements an interface. An interface is an abstract class that only contains method signatures and constant declarations. An interface doesn't contain method definitions and can't be instantiated. A class extends another class. The new class ...
To sum it up, when adding an external jar file in Android Studio: Copy jar to root/project/libs folder; Right-click and add as library; Add the jar to root/project/build.gradle (something like compile files('libs/test-jar-to-import.jar')); Mak...
