diff --git a/app/src/main/java/com/hippo/ehviewer/ui/legacy/SimpleGridLayout.java b/app/src/main/java/com/hippo/ehviewer/ui/legacy/SimpleGridLayout.kt
similarity index 100%
rename from app/src/main/java/com/hippo/ehviewer/ui/legacy/SimpleGridLayout.java
rename to app/src/main/java/com/hippo/ehviewer/ui/legacy/SimpleGridLayout.kt
diff --git a/app/src/main/java/com/hippo/ehviewer/yorozuya/AnimationUtils.java b/app/src/main/java/com/hippo/ehviewer/yorozuya/AnimationUtils.kt
similarity index 100%
rename from app/src/main/java/com/hippo/ehviewer/yorozuya/AnimationUtils.java
rename to app/src/main/java/com/hippo/ehviewer/yorozuya/AnimationUtils.kt
diff --git a/app/src/main/java/com/hippo/ehviewer/yorozuya/ConcurrentPool.java b/app/src/main/java/com/hippo/ehviewer/yorozuya/ConcurrentPool.kt
similarity index 100%
rename from app/src/main/java/com/hippo/ehviewer/yorozuya/ConcurrentPool.java
rename to app/src/main/java/com/hippo/ehviewer/yorozuya/ConcurrentPool.kt
diff --git a/app/src/main/java/com/hippo/ehviewer/yorozuya/IntIdGenerator.java b/app/src/main/java/com/hippo/ehviewer/yorozuya/IntIdGenerator.kt
similarity index 100%
rename from app/src/main/java/com/hippo/ehviewer/yorozuya/IntIdGenerator.java
rename to app/src/main/java/com/hippo/ehviewer/yorozuya/IntIdGenerator.kt