diff --git a/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingLibrary.java b/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingLibrary.java
index 4b41e8bdbc5..a1d608d3cdb 100755
--- a/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingLibrary.java
+++ b/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingLibrary.java
@@ -1,6 +1,7 @@
 package com.minecolonies.core.colony.buildings.workerbuildings;
 
 import com.minecolonies.api.colony.IColony;
+import com.minecolonies.api.util.MathUtils;
 import com.minecolonies.core.colony.buildings.AbstractBuilding;
 import com.minecolonies.core.datalistener.StudyItemListener;
 import net.minecraft.core.BlockPos;
@@ -16,7 +17,6 @@
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Random;
 
 import static com.minecolonies.api.util.constant.NbtTagConstants.TAG_BOOKCASES;
 import static com.minecolonies.api.util.constant.NbtTagConstants.TAG_POS;
@@ -41,11 +41,6 @@ public class BuildingLibrary extends AbstractBuilding
      */
     private final List<BlockPos> bookCases = new ArrayList<>();
 
-    /**
-     * Random obj for random calc.
-     */
-    private final Random random = new Random();
-
     /**
      * Instantiates the building.
      *
@@ -119,7 +114,7 @@ public BlockPos getRandomBookShelf()
         {
             return getPosition();
         }
-        final BlockPos returnPos = bookCases.get(random.nextInt(bookCases.size()));
+        final BlockPos returnPos = bookCases.get(MathUtils.RANDOM.nextInt(bookCases.size()));
         if (colony.getWorld().getBlockState(returnPos).is(Tags.Blocks.BOOKSHELVES))
         {
             return returnPos;
diff --git a/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingUniversity.java b/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingUniversity.java
index 65f45c250e3..50ce10cbcf0 100755
--- a/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingUniversity.java
+++ b/src/main/java/com/minecolonies/core/colony/buildings/workerbuildings/BuildingUniversity.java
@@ -5,6 +5,7 @@
 import com.minecolonies.api.colony.jobs.ModJobs;
 import com.minecolonies.api.research.IGlobalResearchTree;
 import com.minecolonies.api.research.ILocalResearch;
+import com.minecolonies.api.util.MathUtils;
 import com.minecolonies.api.util.MessageUtils;
 import com.minecolonies.core.colony.buildings.AbstractBuilding;
 import com.minecolonies.core.colony.buildings.modules.WorkerBuildingModule;
@@ -50,11 +51,6 @@ public class BuildingUniversity extends AbstractBuilding
      */
     private final List<BlockPos> bookCases = new ArrayList<>();
 
-    /**
-     * Random obj for random calc.
-     */
-    private final Random random = new Random();
-
     /**
      * Instantiates the building.
      *
@@ -121,7 +117,7 @@ public BlockPos getRandomBookShelf()
         {
             return getPosition();
         }
-        final BlockPos returnPos = bookCases.get(random.nextInt(bookCases.size()));
+        final BlockPos returnPos = bookCases.get(MathUtils.RANDOM.nextInt(bookCases.size()));
         if (colony.getWorld().getBlockState(returnPos).is(Tags.Blocks.BOOKSHELVES))
         {
             return returnPos;
diff --git a/src/main/java/com/minecolonies/core/entity/ai/workers/education/EntityAIStudy.java b/src/main/java/com/minecolonies/core/entity/ai/workers/education/EntityAIStudy.java
index 439998d5068..dee2f982caa 100755
--- a/src/main/java/com/minecolonies/core/entity/ai/workers/education/EntityAIStudy.java
+++ b/src/main/java/com/minecolonies/core/entity/ai/workers/education/EntityAIStudy.java
@@ -14,17 +14,13 @@
 import com.minecolonies.core.entity.ai.workers.AbstractEntityAISkill;
 import com.minecolonies.core.entity.pathfinding.navigation.PathfindingAIHelper;
 import net.minecraft.core.BlockPos;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.sounds.SoundEvents;
 import net.minecraft.world.InteractionHand;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.Items;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import static com.minecolonies.api.entity.ai.statemachine.states.AIWorkerState.*;
 import static com.minecolonies.api.util.constant.Constants.TICKS_SECOND;
@@ -117,12 +113,12 @@ private IAIState study()
             return getState();
         }
 
-        final Map<ResourceLocation, StudyItem> studyItems = StudyItemListener.getAllStudyItems();
+        final Collection<StudyItem> studyItems = StudyItemListener.getAllStudyItems().values();
 
         // Search for Items to use to study
         final List<StudyItem> availableItemKeys = new ArrayList<>();
         final Map<StudyItem, Integer> availableItems = new HashMap<>();
-        for (final StudyItem curItem : studyItems.values())
+        for (final StudyItem curItem : studyItems)
         {
             final int slot = InventoryUtils.findFirstSlotInProviderNotEmptyWith(worker, (item) -> item.is(curItem.item()));
             if (slot != -1)
@@ -136,7 +132,7 @@ private IAIState study()
         if (availableItems.isEmpty())
         {
             final List<ItemStack> itemsToRequest = new ArrayList<>();
-            for (final StudyItem studyItem : studyItems.values())
+            for (final StudyItem studyItem : studyItems)
             {
                 final int bSlot = InventoryUtils.findFirstSlotInProviderWith(building, studyItem.item());
                 if (bSlot > -1)