diff --git a/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsBackendWriter.java b/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsBackendWriter.java
index 6029063..6a35e9a 100644
--- a/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsBackendWriter.java
+++ b/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsBackendWriter.java
@@ -1,5 +1,7 @@
 package fr.pandacube.lib.core.permissions;
 
+import java.util.Objects;
+
 import com.google.common.base.Preconditions;
 
 import fr.pandacube.lib.core.db.DB;
@@ -10,9 +12,9 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	
 	
 	/* package */ void addSelfPermission(String name, EntityType type, String permission, String server, String world) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
-		Preconditions.checkNotNull(permission, "permission cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
+		Objects.requireNonNull(permission, "permission cannot be null");
 		Preconditions.checkArgument(world == null || server != null, "world not null but server is null");
 		name = name.toLowerCase();
 		permission = permission.toLowerCase();
@@ -25,9 +27,9 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	}
 	
 	/* package */ void removeSelfPermission(String name, EntityType type, String permission, String server, String world) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
-		Preconditions.checkNotNull(permission, "permission cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
+		Objects.requireNonNull(permission, "permission cannot be null");
 		Preconditions.checkArgument(world == null || server != null, "world not null but server is null");
 		name = name.toLowerCase();
 		permission = permission.toLowerCase();
@@ -47,7 +49,7 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	
 	
 	/* package */ void setGroupDefault(String name, boolean deflt) {
-		Preconditions.checkNotNull(name, "name cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
 		name = name.toLowerCase();
 		try {
 			SQLPermissions entry = DB.getFirst(SQLPermissions.class,
@@ -85,8 +87,8 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	
 	
 	/* package */ void setSelfPrefix(String name, EntityType type, String prefix) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
 		name = name.toLowerCase();
 		
 		try {
@@ -118,8 +120,8 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	}
 	
 	/* package */ void setSelfSuffix(String name, EntityType type, String suffix) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
 		name = name.toLowerCase();
 		
 		try {
@@ -155,9 +157,9 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 
 	
 	/* package */ void addInheritance(String name, EntityType type, String inheritance) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
-		Preconditions.checkNotNull(inheritance, "inheritance cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
+		Objects.requireNonNull(inheritance, "inheritance cannot be null");
 		name = name.toLowerCase();
 		inheritance = inheritance.toLowerCase();
 		String key = type == EntityType.Group ? "inheritances" : "groups";
@@ -179,9 +181,9 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	}
 	
 	/* package */ void removeInheritance(String name, EntityType type, String inheritance) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
-		Preconditions.checkNotNull(inheritance, "inheritance cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
+		Objects.requireNonNull(inheritance, "inheritance cannot be null");
 		name = name.toLowerCase();
 		inheritance = inheritance.toLowerCase();
 		String key = type == EntityType.Group ? "inheritances" : "groups";
@@ -201,9 +203,9 @@ import fr.pandacube.lib.core.permissions.SQLPermissions.EntityType;
 	}
 	
 	/* package */ void setInheritance(String name, EntityType type, String inheritance) {
-		Preconditions.checkNotNull(name, "name cannot be null");
-		Preconditions.checkNotNull(type, "type cannot be null");
-		Preconditions.checkNotNull(inheritance, "inheritance cannot be null");
+		Objects.requireNonNull(name, "name cannot be null");
+		Objects.requireNonNull(type, "type cannot be null");
+		Objects.requireNonNull(inheritance, "inheritance cannot be null");
 		name = name.toLowerCase();
 		inheritance = inheritance.toLowerCase();
 		String key = type == EntityType.Group ? "inheritances" : "groups";
diff --git a/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsResolver.java b/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsResolver.java
index cdf2b91..e583c51 100644
--- a/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsResolver.java
+++ b/Core/src/main/java/fr/pandacube/lib/core/permissions/PermissionsResolver.java
@@ -80,8 +80,8 @@ public class PermissionsResolver {
 			.build();
 	
 	private String getEffectiveData(String name, EntityType type, DataType dataType) {
-		Preconditions.checkNotNull(name, "name can’t be null");
-		Preconditions.checkNotNull(type, "type can’t be null");
+		Objects.requireNonNull(name, "name can’t be null");
+		Objects.requireNonNull(type, "type can’t be null");
 		
 		try {
 			return effectiveDataCache.get(new DataCacheKey(name, type, dataType), () -> {
@@ -239,8 +239,8 @@ public class PermissionsResolver {
 			.build();
 	
 	/* package */ Map<String, Boolean> getEffectivePermissionList(String name, EntityType type, String server, String world) {
-		Preconditions.checkNotNull(name, "name can’t be null");
-		Preconditions.checkNotNull(type, "type can’t be null");
+		Objects.requireNonNull(name, "name can’t be null");
+		Objects.requireNonNull(type, "type can’t be null");
 		Preconditions.checkArgument(world == null || server != null, "world not null but server is null");
 		
 		String fServer = server == null ? null : server.toLowerCase();
@@ -271,9 +271,9 @@ public class PermissionsResolver {
 			.build();
 	
 	/* package */ Boolean getEffectivePermission(String name, EntityType type, String permission, String server, String world) {
-		Preconditions.checkNotNull(name, "name can’t be null");
-		Preconditions.checkNotNull(type, "type can’t be null");
-		Preconditions.checkNotNull(permission, "permission can’t be null");
+		Objects.requireNonNull(name, "name can’t be null");
+		Objects.requireNonNull(type, "type can’t be null");
+		Objects.requireNonNull(permission, "permission can’t be null");
 		Preconditions.checkArgument(world == null || server != null, "world not null but server is null");
 		
 		boolean reversed = false;
diff --git a/Core/src/main/java/fr/pandacube/lib/core/players/IPlayerManager.java b/Core/src/main/java/fr/pandacube/lib/core/players/IPlayerManager.java
index 6c0fc5b..761ea8f 100644
--- a/Core/src/main/java/fr/pandacube/lib/core/players/IPlayerManager.java
+++ b/Core/src/main/java/fr/pandacube/lib/core/players/IPlayerManager.java
@@ -5,10 +5,10 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 
-import com.google.common.base.Preconditions;
 import com.google.common.cache.CacheBuilder;
 import com.google.common.cache.CacheLoader;
 import com.google.common.cache.LoadingCache;
@@ -151,7 +151,7 @@ public abstract class IPlayerManager<OP extends IOnlinePlayer, OF extends IOffPl
 	 * @throws IllegalArgumentException if message is null.
 	 */
 	public static void broadcast(BaseComponent message, boolean prefix, boolean console, String permission, UUID sourcePlayer) {
-		Preconditions.checkNotNull(message, "message cannot be null");
+		Objects.requireNonNull(message, "message cannot be null");
 		
 		IOffPlayer oSourcePlayer = getInstance().getOffline(sourcePlayer);
 		
@@ -310,7 +310,7 @@ public abstract class IPlayerManager<OP extends IOnlinePlayer, OF extends IOffPl
 	 * @throws IllegalArgumentException if message is null.
 	 */
 	public static void broadcast(Chat message, boolean prefix, boolean console, String permission, UUID sourcePlayer) {
-		Preconditions.checkNotNull(message, "message cannot be null");
+		Objects.requireNonNull(message, "message cannot be null");
 		broadcast(message.get(), prefix, console, permission, sourcePlayer);
 	}
 
diff --git a/Core/src/main/java/fr/pandacube/lib/core/search/SearchEngine.java b/Core/src/main/java/fr/pandacube/lib/core/search/SearchEngine.java
index 2a340c4..3d51132 100644
--- a/Core/src/main/java/fr/pandacube/lib/core/search/SearchEngine.java
+++ b/Core/src/main/java/fr/pandacube/lib/core/search/SearchEngine.java
@@ -5,12 +5,12 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.stream.Collectors;
 
-import com.google.common.base.Preconditions;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
 
@@ -48,7 +48,7 @@ public class SearchEngine<R extends SearchResult> {
 		Set<String> searchKw;
 		try {
 			searchKw = result.getSearchKeywords();
-			Preconditions.checkNotNull(searchKw, "SearchResult instance must provide a non null set of search keywords");
+			Objects.requireNonNull(searchKw, "SearchResult instance must provide a non null set of search keywords");
 			searchKw = searchKw.stream()
 					.filter(e -> e != null)
 					.map(String::toLowerCase)
@@ -61,7 +61,7 @@ public class SearchEngine<R extends SearchResult> {
 		Set<String> suggestsKw;
 		try {
 			suggestsKw = result.getSuggestionKeywords();
-			Preconditions.checkNotNull(suggestsKw, "SearchResult instance must provide a non null set of suggestions keywords");
+			Objects.requireNonNull(suggestsKw, "SearchResult instance must provide a non null set of suggestions keywords");
 			suggestsKw = new HashSet<>(suggestsKw);
 			suggestsKw.removeIf(e -> e == null);
 		} catch (Exception e) {