HttpClientBuilder is no longer supported on Android starting SDK version 23.

[scimetfoo]

It isn't possible to instantiate RedditClient with HttpClientBuilder anymore, if an Android project is using the latest SDK. Maybe it's time to start migrating toOkHttpClient?

RedditClient client = new RedditHttpClient(REDDIT_USER_AGENT, HttpClientBuilder.create().build());

is no longer supported.

[theshapguy]

You'll need to add

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.0"
//The following line
    useLibrary 'org.apache.http.legacy'
    ...
}

[hmble]

As shown in this SO answer by user Jinu

If you are using target sdk as 23 add below code in your build.gradle

android{
    compileSdkVersion 23
    buildToolsVersion '23.0.1'
    useLibrary  'org.apache.http.legacy'
}

and change your buildscript to

classpath 'com.android.tools.build:gradle:1.3.0' 

For more info follow this link