How some parts of activity's store in external class on Android?

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http://stackoverflow.com – Assume that i have a activity class named MainActivity.java. But this activity has about 3000 lines code for example. I want to seperate code parts of this file to an external java file(class) named NecessaryThings.java. But if i run my project on emulator it stops itself after this operation. Is there a way to seperate some lines of this activity? I wrote mini example for better.. Also what do you think about; Using this method is beneficial or harmful in terms of performance? This is my MainActivity.java public class MainActivity extends Activity { @Override protected void onCre (HowTos)