diff --git a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/ChangePayloadProducer.java b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/ChangePayloadProducer.java
index 78f4319..ffbbb03 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/ChangePayloadProducer.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/ChangePayloadProducer.java
@@ -22,8 +22,20 @@ package ru.touchin.roboswag.core.observables.collections.changes;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 
+/**
+ * Functional interface for calculating change payload between two items same type.
+ * Payload calculating when items are same {@link SameItemsPredicate}, but content different.
+ */
 public interface ChangePayloadProducer<TItem> {
 
+
+    /**
+     * Calculate change payload between two items.
+     *
+     * @param item1 First item;
+     * @param item2 Second item;
+     * @return Object that represents minimal changes between two items.
+     */
     @Nullable
     Object getChangePayload(@NonNull TItem item1, @NonNull TItem item2);
 
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/CollectionsChangesCalculator.java b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/CollectionsChangesCalculator.java
index d86147d..9f6d026 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/CollectionsChangesCalculator.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/CollectionsChangesCalculator.java
@@ -23,14 +23,32 @@ import android.support.annotation.NonNull;
 
 import java.util.List;
 
+/**
+ * Interface that represent changes calculator between two collections.
+ */
 public interface CollectionsChangesCalculator<TItem> {
 
+    /**
+     * Calculate changes between two collection as collection of objects {@link Change}.
+     *
+     * @return List of changes.
+     */
     @NonNull
     List<Change> calculateChanges();
 
+    /**
+     * Calculate changes between two collection as collection of inserted items.
+     *
+     * @return List of inserted item.
+     */
     @NonNull
     List<TItem> calculateInsertedItems();
 
+    /**
+     * Calculate changes between two collection as collection of removed items.
+     *
+     * @return List of removed item.
+     */
     @NonNull
     List<TItem> calculateRemovedItems();
 
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DefaultCollectionsChangesCalculator.java b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DefaultCollectionsChangesCalculator.java
index 883fed8..09cd790 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DefaultCollectionsChangesCalculator.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DefaultCollectionsChangesCalculator.java
@@ -25,6 +25,9 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
+/**
+ * Default calculator between two collections that use equals function.
+ */
 public class DefaultCollectionsChangesCalculator<TItem> implements CollectionsChangesCalculator<TItem> {
 
     @NonNull
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DiffCollectionsChangesCalculator.java b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DiffCollectionsChangesCalculator.java
index 9115e6c..7b72772 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DiffCollectionsChangesCalculator.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/DiffCollectionsChangesCalculator.java
@@ -28,6 +28,9 @@ import java.util.List;
 import ru.touchin.roboswag.core.android.support.v7.util.DiffUtil;
 import ru.touchin.roboswag.core.android.support.v7.util.ListUpdateCallback;
 
+/**
+ * Implementation of {@link CollectionsChangesCalculator} based on DiffUtils from support library.
+ */
 public class DiffCollectionsChangesCalculator<TItem> extends DiffUtil.Callback implements CollectionsChangesCalculator<TItem> {
 
     @NonNull
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/SameItemsPredicate.java b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/SameItemsPredicate.java
index 1cb03da..611f6a5 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/SameItemsPredicate.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/collections/changes/SameItemsPredicate.java
@@ -21,8 +21,20 @@ package ru.touchin.roboswag.core.observables.collections.changes;
 
 import android.support.annotation.NonNull;
 
+/**
+ * Functional interface for determine same objects. Usually this is just the comparison by id.
+ *
+ * @param <TItem> Type of objects
+ */
 public interface SameItemsPredicate<TItem> {
 
+    /**
+     * Function for determine same objects.
+     *
+     * @param item1 First object;
+     * @param item2 Second object;
+     * @return True if items are same.
+     */
     boolean areSame(@NonNull TItem item1, @NonNull TItem item2);
 
 }