Enum variant to handle switching of environments. I had previously implemented PushConfig.java as an abstract class and had QaPushConfig.java and ProdPushConfig.java extend them, but that resulted in ugly switch-case logic everywhere I wanted to use them. Patrick refactored that implementation into what you see below.

MyApplication.java

public class MyApplication extends Application {

    public static final PushConfig.Environment ENVIRONMENT = PushConfig.Environment.PROD; // can also be .QA
    private static final String TAG = "MyApplication";

    @Override
    public void onCreate() {
        super.onCreate();
        final PushConfig pushConfig = ENVIRONMENT.getPushConfig();
        String appId = pushConfig.etAppId;
        String url = pushConfig.restEndPoint;
        String gcmSenderId = pushConfig.gcmSenderId;
        // Do something with those values ...
    }
}

Preconditions.java

/**
 * Just a helper class to validate data.  Can be largely ignored.
 * 
 * Created by billmote on 4/26/15.
 */
public final class Preconditions {

    private Preconditions() {
        throw new AssertionError("No instances.");
    }

    public static void checkArgument(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalArgumentException(String.valueOf(errorMessage));
        }
    }

    public static void checkState(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    public static <T> T checkNotNull(T reference, String name) {
        if (reference == null) {
            throw new NullPointerException(name + " must not be null");
        }
        return reference;
    }

    public static <T extends CharSequence> T checkNotBlank(T value, String name) {
        if (TextUtils.isEmpty(value)) {
            throw new IllegalArgumentException(name + " must not be blank");
        }
        return value;
    }
}

PushConfig.java

/**
 * Created by bmote on 4/16/15.
 */
public abstract class PushConfig {
    public String gcmSenderId = "0123456789";
    public String restEndPoint;
    public String etAppId;

    public void validateFields() {
        Preconditions.checkNotBlank(gcmSenderId, "PushConfig.gcmSenderId");
        Preconditions.checkNotBlank(restEndPoint, "PushConfig.restEndPoint");
        Preconditions.checkNotBlank(etAppId, "PushConfig.etAppId");
    }

    public enum Environment {
        QA {
            @Override
            public PushConfig getPushConfig() {
                return new QaPushConfig();
            }
        },
        PROD {
            @Override
            public PushConfig getPushConfig() {
                return new ProdPushConfig();
            }
        };

        public abstract PushConfig getPushConfig();
    }

    private static class QaPushConfig extends PushConfig {

        private static final String TAG = "QaPushConfig";

        public QaPushConfig() {
            Log.i(TAG, String.format("Using %1$s Configuration", TAG));
            restEndPoint = "http://qa.mysite.com/";
            etAppId = "some-crazy-guid";
            validateFields();
        }
    }

    private static class ProdPushConfig extends PushConfig {

        private static final String TAG = "ProdPushConfig";

        public ProdPushConfig() {
            Log.i(TAG, String.format("Using %1$s Configuration", TAG));
            restEndPoint = "http://www.mysite.com/";
            etAppId = "some-other-crazy-id";
            validateFields();
        }
    }
}

SomeClass.java

public class SomeClass {

    public static final String TAG = "ServiceEventHandler";
    private final PushConfig pushConfig;

    public SomeClass() {
        pushConfig = MyApplication.ENVIRONMENT.getPushConfig();
    }

    /**
     * Get stuff
     */
    public void getStuff(final GetStuffRequest request) {
        // use pushConfig.restEndPoint or others here :)
    }
}