How to make a quick start the android emulator

Button btn.setBackgroundResource(R.drawable.back_button_answer);

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="//schemas.android.com/apk/res/android" android:shape="rectangle" >
   <corners android:radius="10dip" />
   <!-- background -->
   
   <gradient
                android:startColor="#D6D7D6"
                android:centerColor="#E2E2E2"
                android:centerY="0.75"
                android:endColor="#D6D7D6"
                android:angle="270"
        />
   
   <stroke android:width="2dip" android:color="#fff"/>
</shape>

import java.util.ArrayList;
import java.util.Collections;

public class MainClass {
	public static void main(String[] arg) {
		String[] arrayOfString = {"nothing", "Hello", "people"
				, "bye-bye", "hello", "world!", "End" };
		   ArrayList<String> arrayList = new ArrayList<String>();
            for(String s: arrayOfString)
		     arrayList.add(s);

		    Collections.sort(arrayList);
		    // foreach
		    for (String str: arrayList)
		      System.out.println(str);
		    
		    Object objMin = Collections.min(arrayList);
		    System.out.println("Min is: " + objMin);
		    
		    Object objMax = Collections.max(arrayList);
		    System.out.println("Max is: " + objMax);
		    
		    int index = Collections.binarySearch(arrayList, "people");
		    System.out.println("Index of people is: " + index);
		    
		  }

		
	
}
/*
End
Hello
bye-bye
hello
nothing
people
world!
Min is: End
Max is: world!
Index of people is: 5
*/

import android.content.Context;
import android.media.AudioManager;
import android.media.SoundPool;

public class SoundManager
{
  private SoundPool soundPool;
  private int[] sm;
  Context context;

  public SoundManager(Context context) {
    this.context = context;
    soundPool = new SoundPool(4, AudioManager.STREAM_MUSIC, 0);
    sm = new int[2];
    // fill your sounds
    sm[0] = soundPool.load(context, R.raw.my_sound1, 1);
    sm[1] = soundPool.load(context, R.raw.my_sound2, 1);
  }

  public final void playSound(int sound) {
      AudioManager mgr = (AudioManager)context.getSystemService(
          Context.AUDIO_SERVICE);  
      float streamVolumeCurrent =
          mgr.getStreamVolume(AudioManager.STREAM_MUSIC);
      float streamVolumeMax = mgr.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
      float volume = streamVolumeCurrent / streamVolumeMax;
      soundPool.play(sm[sound], volume, volume, 1, 0, 1f);
  }

  public final void cleanUpIfEnd() {
    sm = null;
    context = null;
    soundPool.release();
    soundPool = null;
  }
}

1. open AVD MANAGER


2. press Create Virtual Device


3. select Device with small memory usage (e.g. 480x800 of resolution) - Next


4. check - Show downloadable ....


5. Download - lower version of system Android, select, press - Next


6. check data, Show Advanced Settings, check Use host... and press Finish