Helper class for most important and basic methods for any Android App.

Utils.java

public class Utils {
  
  /*
   * Usage: Check if device have internet connection or not, before communicating with server.
   * @param ctx: Context form which this method will be called
   * @return Boolean: If internet is available or not.
  */
  public static boolean isNetConnected(Context ctx) {
        Runtime runtime = Runtime.getRuntime();
        try {
            Process ipProcess = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
            int exitValue = ipProcess.waitFor();
            return (exitValue == 0);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return false;
    }
    
    /*
     * Usage: Convert a Byte array to Hexa decimal String
     * @param bytes: Input byte array
     * @return String: Hexadecimal string
    */
    public static String bytesArrayToHexString(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for (int j = 0; j < bytes.length; j++) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }
    
    /*
     * Usage: Get MD5 representation of any String
     * @param data: Input String
     * @return String: MD5 string
    */
    public static String getMd5(String data) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            return bytesArrayToHexString(md.digest(data.getBytes("UTF-8")));
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
    
    /*
     * Usage: Get Bitmap for given File
     * @param file: Input File
     * @return Bitmap: Bitmap image
    */
    public static Bitmap getBitmapFromFile(File file) {
        try {
            if (!file.exists()) {
                return null;
            }
            return BitmapFactory.decodeFile(file.getPath());
        } catch (Exception e) {
            return null;
        }
    }
    
    /*
     * Usage: Convert String to Base64 String
     * @param input: Input String
     * @return String: Base64 representation of String
    */
    public static String encodeBase64(String input) {
        byte[] data = new byte[0];
        try {
            data = input.getBytes("UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return Base64.encodeToString(data, Base64.NO_PADDING);
    }
    
    /*
     * Usage: Decode Base64 String to String
     * @param input: Input Base64 version of String
     * @return String: String decoded form Base64
    */
    public static String decodeBase64(String input) {
        byte[] data = Base64.decode(input, Base64.NO_PADDING);
        try {
            return new String(data, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return null;
    }
    
    /*
     * Usage: To check whether device have removable external storage
     * @return Boolean: if device has removable external storage or not
    */
    public static boolean isExternalStorageRemovable() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
            return Environment.isExternalStorageRemovable();
        }
        return true;
    }
    
    /*
     * Usage: Check whether device is connected to wifi or not
     * @param ctx: Context of calling method
     * @return Boolean: true if device is connected to wifi, else false
    */
    public static boolean isWifiConnected(Context ctx) {
        ConnectivityManager connManager = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetwork = connManager.getActiveNetworkInfo();
        if (activeNetwork != null) { // connected to the internet
            if (activeNetwork.getType() == ConnectivityManager.TYPE_WIFI) {
                // Connected to wifi
                return true;
            } else if (activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE) {
                // Connected to the mobile provider's data plan
                return false;
            }
        } else {
            // Not connected to the internet
            return false;
        }
        return false;
    }
    
    /*
     * Usage: Generate random number of given length
     * @param length: length of required random number
     * @return String: Random number in String type of input length
    */
    public static String generateRandomNumber(int length) {
        Random random = new Random();
        char[] digits = new char[length];
        digits[0] = (char) (random.nextInt(9) + '1');
        for (int i = 1; i < length; i++) {
            digits[i] = (char) (random.nextInt(10) + '0');
        }
        return new String(digits);
    }
    
    /*
     * Usage: Check whether your service is running or not
     * @param ctx: Context of calling method
     * @param serviceClass: Class of service which needs to be checked
     * @return Boolean: true if given service class is running, else false
    */
    public static boolean isMyServiceRunning(Context ctx, Class<?> serviceClass) {
		  ActivityManager manager = (ActivityManager) ctx.getSystemService(Context.ACTIVITY_SERVICE);
		  for (RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
			  if (serviceClass.getName().equals(service.service.getClassName())) {
				  return true;
			  }
		  }
		  return false;
	}
	
	/*
     * Usage: To find nth occurrence of a character in given String
     * @param str: input String in which to find character occurrence 
     * @param chars: characters to be searched in String
     * @param n: required nth occurrence
     * @return Int: Position of nth occurrence of chars in input String
    */
	public static int nthOccurrence(String str, String chars, int n) {
		int pos = str.indexOf(chars, 0);
		while (n-- > 0 && pos != -1)
			pos = str.indexOf(chars, pos + 1);
		return pos;
	}
	
	/*
   * Usage: Show Toast message to user.
   * @param ctx: Context of calling method
   * @param msg: Message to be displayed in Toast.
   */
  public static void showToast(Context ctx, String msg) {
    Toast.makeText(ctx, msg, Toast.LENGTH_SHORT).show();
  }
  
  /**
   * Usage: Check whether device is tablet or phone
   * @param context: Context of Calling method
   * @return Boolean: true if device is tablet, else false
   */
  public static boolean isTablet(Context context) {
  	boolean xlarge = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == 4);
       	boolean large = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE);
       	return (xlarge || large);
  }
}