diff --git a/src/main/idea/io/github/linwancen/plugin/show/java/doc/AnnoDoc.java b/src/main/idea/io/github/linwancen/plugin/show/java/doc/AnnoDoc.java
index 6f6a107..12a8a00 100644
--- a/src/main/idea/io/github/linwancen/plugin/show/java/doc/AnnoDoc.java
+++ b/src/main/idea/io/github/linwancen/plugin/show/java/doc/AnnoDoc.java
@@ -19,6 +19,8 @@ import org.jetbrains.annotations.Nullable;
 
 public class AnnoDoc {
 
+    private AnnoDoc() {}
+
     @Nullable
     public static <T extends SettingsInfo> String annoDoc(@NotNull T info, @NotNull PsiJvmModifiersOwner owner) {
         @NotNull ProjectSettingsState projectSettings = info.projectSettings;
diff --git a/src/main/idea/io/github/linwancen/plugin/show/java/doc/EnumDoc.java b/src/main/idea/io/github/linwancen/plugin/show/java/doc/EnumDoc.java
index 5059bc0..6b347ae 100644
--- a/src/main/idea/io/github/linwancen/plugin/show/java/doc/EnumDoc.java
+++ b/src/main/idea/io/github/linwancen/plugin/show/java/doc/EnumDoc.java
@@ -11,6 +11,8 @@ import java.util.stream.Collectors;
 
 public class EnumDoc {
 
+    private EnumDoc() {}
+
     /**
      * Yes(1, "Yes") show 1-Yes
      */
diff --git a/src/main/idea/io/github/linwancen/plugin/show/java/doc/NewDoc.java b/src/main/idea/io/github/linwancen/plugin/show/java/doc/NewDoc.java
index 535be16..06fde25 100644
--- a/src/main/idea/io/github/linwancen/plugin/show/java/doc/NewDoc.java
+++ b/src/main/idea/io/github/linwancen/plugin/show/java/doc/NewDoc.java
@@ -7,6 +7,9 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class NewDoc {
+
+    private NewDoc() {}
+
     @Nullable
     public static PsiMethod newMethod(@NotNull PsiElement ref) {
         PsiElement parent = ref.getParent();
diff --git a/src/main/idea/io/github/linwancen/plugin/show/java/doc/ParamDoc.java b/src/main/idea/io/github/linwancen/plugin/show/java/doc/ParamDoc.java
index c202140..012585d 100644
--- a/src/main/idea/io/github/linwancen/plugin/show/java/doc/ParamDoc.java
+++ b/src/main/idea/io/github/linwancen/plugin/show/java/doc/ParamDoc.java
@@ -11,6 +11,9 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class ParamDoc {
+
+    private ParamDoc() {}
+
     @Nullable
     public static String paramDoc(@NotNull PsiParameter psiParameter) {
         @Nullable PsiMethod method = PsiTreeUtil.getParentOfType(psiParameter, PsiMethod.class);
diff --git a/src/main/java/io/github/linwancen/plugin/show/cache/LineEndCacheUtils.java b/src/main/java/io/github/linwancen/plugin/show/cache/LineEndCacheUtils.java
index 10b45fe..54fdb22 100644
--- a/src/main/java/io/github/linwancen/plugin/show/cache/LineEndCacheUtils.java
+++ b/src/main/java/io/github/linwancen/plugin/show/cache/LineEndCacheUtils.java
@@ -22,6 +22,9 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 
 public class LineEndCacheUtils {
+
+    private LineEndCacheUtils() {}
+
     private static final Logger LOG = LoggerFactory.getLogger(LineEndCacheUtils.class);
 
     public static final Map<Project, Map<VirtualFile, Map<Integer, LineEndCache>>> cache = new ConcurrentHashMap<>();
diff --git a/src/main/java/io/github/linwancen/plugin/show/cache/TreeCacheUtils.java b/src/main/java/io/github/linwancen/plugin/show/cache/TreeCacheUtils.java
index 4079cd1..65bbab4 100644
--- a/src/main/java/io/github/linwancen/plugin/show/cache/TreeCacheUtils.java
+++ b/src/main/java/io/github/linwancen/plugin/show/cache/TreeCacheUtils.java
@@ -17,6 +17,9 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 
 public class TreeCacheUtils {
+
+    private TreeCacheUtils() {}
+
     private static final Logger LOG = LoggerFactory.getLogger(TreeCacheUtils.class);
 
     public static final Map<Project, Map<ProjectViewNode<?>, TreeCache>> cache = new ConcurrentHashMap<>();
diff --git a/src/main/java/io/github/linwancen/plugin/show/line/LineSelect.java b/src/main/java/io/github/linwancen/plugin/show/line/LineSelect.java
index 791cca9..658143a 100644
--- a/src/main/java/io/github/linwancen/plugin/show/line/LineSelect.java
+++ b/src/main/java/io/github/linwancen/plugin/show/line/LineSelect.java
@@ -9,6 +9,9 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class LineSelect {
+
+    private LineSelect() {}
+
     /**
      * can not work
      */