URLUtils.java

public class URLUtils {

  private static final String fGOOGLE_DOC_URL = "http://docs.google.com/gview?embedded=true&url=%s";

  private enum GoogleDocType{
    PDF(".pdf"), DOC(".doc"), XLS(".xls"), DOCX(".docx"), XLSX(".xlsx");

    private String mSuffix;
    GoogleDocType(String suffix){
      mSuffix = suffix;
    }

    private boolean isTypeOf(String url){
      return url.endsWith(mSuffix);
    }
  }


  public static String buildGoogleDocURL(String url){
    if(TextUtils.isEmpty(url)) return null;

    for(GoogleDocType type : GoogleDocType.values())
      if(type.isTypeOf(url))
        return String.format(fGOOGLE_DOC_URL, url);

    return url;
  }
}