read file from assets

public class Utils {
    public static List<Message> getMessages() {
        //File file = new File("file:///android_asset/helloworld.txt");
        AssetManager assetManager = getAssets();
        InputStream ims = assetManager.open("helloworld.txt");    
     }
}

I am using this code trying to read a file from assets. I tried two ways to do this. First, when use File I received FileNotFoundException, when using AssetManager getAssets() method isn’t recognized.
Is there any solution here?