CaUtil.java

public class CaUtil {

    private static final String TAG = "Tag.CaUtil";

    public static String getCaString(Context context) {
        try {
            /* Get certificate string (for HTTPS connection) */
            InputStream caInput = new BufferedInputStream(context.getAssets().open("customCA.crt"));
            InputStreamReader inputStreamReader = new InputStreamReader(caInput);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String line;
            StringBuilder builder = new StringBuilder("");
            while ((line = bufferedReader.readLine()) != null) {
                builder.append(line + "\n");
            }
            return builder.toString();
        } catch (Exception e) {
            Log.d(TAG, "getCaString: e: " + e.getMessage());
            e.printStackTrace();
            return null;
        }
    }
}