Prevent creation of some internal-only classes

Author: marcinqualaroo

src/main/java/com/filestack/FileLink.java

@@ -33,8 +33,10 @@ public class FileLink implements Serializable {
   protected final String handle;
 
   /**
+   * Basic constructor for a FileLink.
+   *
    * @deprecated FileLink objects should not be created by hand - use {@link Client} to acquire them.
-   * This method is scheduled to be removed in version 1.0.0.
+   *     This method is scheduled to be removed in version 1.0.0.
    */
   @Deprecated
   public FileLink(Config config, String handle) {

src/main/java/com/filestack/Progress.java

@@ -10,6 +10,8 @@ public class Progress<T> {
   private final T data;
 
   /**
+   * Basic constructor for Progress.
+   * 
    * @deprecated access to this constructor is scheduled to be limited in 1.0.0 to internal use only.
    */
   @Deprecated

src/main/java/com/filestack/internal/CloudServiceUtil.java

@@ -74,4 +74,7 @@ public static void addStorageJson(JsonObject base, String cloud, StorageOptions
 
     base.getAsJsonObject(KEY_CLOUDS).getAsJsonObject(cloud).add(KEY_STORE, json);
   }
+
+  private CloudServiceUtil() {}
+
 }

src/main/java/com/filestack/internal/HeaderInterceptor.java

@@ -18,7 +18,7 @@ public class HeaderInterceptor implements Interceptor {
 
   private String version;
 
-  public HeaderInterceptor() {
+  HeaderInterceptor() {
     this.version = Util.getVersion();
   }
 

src/main/java/com/filestack/internal/Networking.java

@@ -2,6 +2,7 @@
 
 import java.util.concurrent.TimeUnit;
 
+import com.google.common.graph.Network;
 import okhttp3.OkHttpClient;
 import retrofit2.Retrofit;
 import retrofit2.converter.gson.GsonConverterFactory;
@@ -10,7 +11,7 @@
  * Holds {@link OkHttpClient} and {@link Retrofit} singletons.
  * We only want to instantiate these classes once per app.
  */
-public class Networking {
+public final class Networking {
   private static OkHttpClient httpClient;
   private static BaseService baseService;
   private static CdnService cdnService;
@@ -115,4 +116,6 @@ private static void invalidateServices() {
     uploadService = null;
     cloudService = null;
   }
+
+  private Networking() {}
 }

src/test/java/com/filestack/internal/TestNetworking.java

@@ -4,7 +4,7 @@
 import org.junit.Assert;
 import org.junit.Test;
 
-public class TestNetworking extends Networking {
+public class TestNetworking {
 
   @Test
   public void testCreation() {