layout id cannot be resolved or is not a field

import java.util.Map;
import java.util.TreeMap;

public class MainClass {
	public static void main(String[] arg) {

		// english;germany dictionary
		String[] arrayOfString = { "one;eine", "two;zwei", "two sets of;zwei"
				, "three;drei", "four;vier" };

		Map<String, String> map = new TreeMap<String, String>();

		for (String s : arrayOfString) {
			String[] array = s.split(";");
			String sKey = "", sValue = "";
			if (array.length > 1) {
				sKey = array[0];
				sValue = array[1];
				map.put(sKey, sValue);
			}
		}
    Object[] objectArrayOfValues = map.values().toArray();
	for (int i = 0; i < objectArrayOfValues.length; i++) {
		System.out.println(objectArrayOfValues[i]);
	}
		 
		
	}// end main

}
/*
vier
eine
drei
zwei
zwei
 */

    private SensorManager mSensorManager;
    private PowerManager mPowerManager;
    private WindowManager mWindowManager;
    private Display mDisplay;

// onCreate
   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

       // Get an instance of the SensorManager
        mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);

        // Get an instance of the PowerManager
        mPowerManager = (PowerManager) getSystemService(POWER_SERVICE);

        // Get an instance of the WindowManager
        mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        mDisplay = mWindowManager.getDefaultDisplay();

        setContentView(R.layout.main); // main.xml or your xml file name

}

// warning
private static String DB_PATH =  "/data/data/cz.okhelp.german_czech_phrases/databases/";

// OK
   public DataBaseHelper(Context context) {	 
    	super(context, DB_NAME, null, 1);
        this.myContext = context;
        // OK
         DB_PATH = context.getFilesDir().getParentFile().getPath()
              + "/databases/";
    }

Window>Preference>Java>Editor>Typing and check the "Escape text when pasting into a string literal".

// single line
/*
multi line
*/