Java Programming Utility Classes

Question

I am new to Java and I talked about my question on the web, but not completely satisfied. I want to know what a "utility class" is in Java?

Someone please tell me an example.

Thanks David

Answer 1

This is usually a class that only has static methods (possibly with a private constructor and tagged abstract / final to prevent instantiation / subclassing). It exists only to simplify the use of other classes, for example, to provide a bunch of static methods for working with values String, to perform additional actions that it Stringdoes not support.

Utility classes do not usually work on classes that you control, because otherwise you usually inject behavior directly into this class. They are not very accurate in terms of OO, but can still be useful.

Answer 2

To extend the response Skeet Jon, java.lang.Math, java.util.Collectionsand java.util.Arraysare typical examples for such classes.

Answer 3

There is a java.util utility package that contains a bunch of things, such as dates, times, string tokenizers ... Not sure if this is what you are talking about.

Answer 4

Its class with all static methods and without member elements.

Answer 5

public class Utils {

public static boolean isNetworkAvailable(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context
            .getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager
            .getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}

public static void unlockScreenOrientation(Activity activity) {
    activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
}

public static void lockScreenOrientation(Activity activity) {
    int currentOrientation = activity.getResources().getConfiguration().orientation;
    if (currentOrientation == Configuration.ORIENTATION_PORTRAIT)
    {
        activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    }
    else
    {
        activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
    }
}
// Get Http Post response
@Nullable
public static String getHttpResponse(String url, List<NameValuePair> nameValuePairs) {
    HttpClient httpClient = new DefaultHttpClient();

    HttpPost httpPost = new HttpPost(url);
    UrlEncodedFormEntity entity;
    try {
        entity = new UrlEncodedFormEntity(nameValuePairs);
        httpPost.setEntity(entity);
        HttpResponse response = httpClient.execute(httpPost);

        HttpEntity resEntity = response.getEntity();
        String res =  EntityUtils.toString(resEntity);
        return res;
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

public static void CopyStream(InputStream is, OutputStream os) {
    final int buffer_size=1024;
    try
    {
        byte[] bytes=new byte[buffer_size];
        for(;;)
        {
            int count=is.read(bytes, 0, buffer_size);
            if(count==-1)
                break;
            os.write(bytes, 0, count);
        }
    }
    catch(Exception ex){}
}

public static JSONObject getJsonObjectFromXmlResponse(String xmlString) {
    JSONObject objectJson = new JSONObject();
    //JSONArray arrayJson = new JSONArray();

    XmlPullParser parser = Xml.newPullParser();
    try {
        parser.setInput(new StringReader(xmlString));
        int eventType = parser.getEventType();

        while (eventType != XmlPullParser.END_DOCUMENT) {
            String name;
            switch (eventType) {
                case XmlPullParser.START_TAG:
                    name = parser.getName();
                    if (name.equalsIgnoreCase("string")) {
                        String yourValue = parser.nextText();
                        //arrayJson = new JSONArray(yourValue);
                        objectJson = new JSONObject(yourValue);
                    }
                    break;
            }
            eventType = parser.next();
        }
    } catch (XmlPullParserException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (JSONException e) {
        e.printStackTrace();
    }
    return objectJson;
}

}