java - How to fix NetworkonMainThreadException in Android?

I'm creating an project for assignment, I'm new to Android, and I wanted to access json from very common url http://api.androidhive.info/contacts/,

Problem: I'm trying to read the url and fetch and parse the json returned by this url,

I've already added following line into my AndroidManifest.xml

Preferences: and my android preferences are

        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

1. Api level 18


2. Android 4.3

and this is how I'm trying to read the url

static InputStream is = null;
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();

The Error Message

11-02 05:23:47.843: E/AndroidRuntime(2207): FATAL EXCEPTION: main
11-02 05:23:47.843: E/AndroidRuntime(2207): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.me.countrypedia/com.me.countrypedia.MainActivity}: android.os.NetworkOnMainThreadException
11-02 05:23:47.843: E/AndroidRuntime(2207):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-02 05:23:47.843: E/AndroidRuntime(2207):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-02 05:23:47.843: E/AndroidRuntime(2207):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-02 05:23:47.843: E/AndroidRuntime(2207):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)

Also I'm following this tutorial for ListView Example
http://www.androidhive.info/2011/11/android-xml-parsing-tutorial/