diff --git a/HMCL/src/main/java/org/jackhuang/hmcl/game/HMCLGameRepository.java b/HMCL/src/main/java/org/jackhuang/hmcl/game/HMCLGameRepository.java
index 4c0146bcf..9177da0d3 100644
--- a/HMCL/src/main/java/org/jackhuang/hmcl/game/HMCLGameRepository.java
+++ b/HMCL/src/main/java/org/jackhuang/hmcl/game/HMCLGameRepository.java
@@ -80,13 +80,6 @@ public class HMCLGameRepository extends DefaultGameRepository {
         }
     }
 
-    @Override
-    public void refreshVersions() {
-        EventBus.EVENT_BUS.fireEvent(new RefreshingVersionsEvent(this));
-        refreshVersionsImpl();
-        EventBus.EVENT_BUS.fireEvent(new RefreshedVersionsEvent(this));
-    }
-
     public void changeDirectory(File newDirectory) {
         setBaseDirectory(newDirectory);
         refreshVersionsAsync().start();
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/DefaultGameRepository.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/DefaultGameRepository.java
index c42edb4b9..f20eda3cf 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/DefaultGameRepository.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/DefaultGameRepository.java
@@ -117,7 +117,7 @@ public class DefaultGameRepository implements GameRepository {
     }
 
     public Version readVersionJson(File file) throws IOException, JsonParseException {
-        return JsonUtils.GSON.fromJson(FileUtils.readText(file), Version.class);
+        return JsonUtils.fromNonNullJson(FileUtils.readText(file), Version.class);
     }
 
     @Override
@@ -221,7 +221,7 @@ public class DefaultGameRepository implements GameRepository {
 
                 Version version;
                 try {
-                    version = Objects.requireNonNull(readVersionJson(json));
+                    version = readVersionJson(json);
                 } catch (Exception e) {
                     LOG.log(Level.WARNING, "Malformed version json " + id, e);
                     // JsonSyntaxException or IOException or NullPointerException(!!)
@@ -229,7 +229,7 @@ public class DefaultGameRepository implements GameRepository {
                         return Stream.empty();
 
                     try {
-                        version = Objects.requireNonNull(readVersionJson(json));
+                        version = readVersionJson(json);
                     } catch (Exception e2) {
                         LOG.log(Level.SEVERE, "User corrected version json is still malformed", e2);
                         return Stream.empty();
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Library.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Library.java
index 49360eca6..73e8a9de3 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Library.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Library.java
@@ -45,13 +45,13 @@ public class Library implements Comparable<Library> {
     private final String classifier;
     private final String url;
     private final LibrariesDownloadInfo downloads;
-    private final LibraryDownloadInfo download;
+    private transient final LibraryDownloadInfo download;
     private final ExtractRules extract;
     private final Map<OperatingSystem, String> natives;
     private final List<CompatibilityRule> rules;
     private final List<String> checksums;
 
-    private final String path;
+    private transient final String path;
 
     public Library(String groupId, String artifactId, String version) {
         this(groupId, artifactId, version, null, null, null);
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/mod/MultiMCModpackInstallTask.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/mod/MultiMCModpackInstallTask.java
index 4dd991b8b..b9c6b06ea 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/mod/MultiMCModpackInstallTask.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/mod/MultiMCModpackInstallTask.java
@@ -40,7 +40,6 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.LinkedList;
 import java.util.List;
-import java.util.Objects;
 import java.util.Optional;
 
 /**
@@ -133,7 +132,7 @@ public final class MultiMCModpackInstallTask extends Task {
     
     @Override
     public void execute() throws Exception {
-        Version version = Objects.requireNonNull(repository.readVersionJson(name));
+        Version version = repository.readVersionJson(name);
 
         try (FileSystem fs = CompressingUtils.createReadOnlyZipFileSystem(zipFile.toPath())) {
             Path root = Files.list(fs.getPath("/")).filter(Files::isDirectory).findAny()
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/Lang.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/Lang.java
index 6d5ee2b82..195d7cf18 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/Lang.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/Lang.java
@@ -17,14 +17,15 @@
  */
 package org.jackhuang.hmcl.util;
 
+import org.jackhuang.hmcl.util.function.ExceptionalRunnable;
+import org.jackhuang.hmcl.util.function.ExceptionalSupplier;
+
 import java.util.*;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Consumer;
-import org.jackhuang.hmcl.util.function.ExceptionalRunnable;
-import org.jackhuang.hmcl.util.function.ExceptionalSupplier;
 
 /**
  *
@@ -203,14 +204,6 @@ public final class Lang {
         }
     }
 
-    public static Double toDoubleOrNull(Object string) {
-        try {
-            return Double.parseDouble(string.toString());
-        } catch (NumberFormatException e) {
-            return null;
-        }
-    }
-
     /**
      * Find the first non-null reference in given list.
      * @param t nullable references list.
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/versioning/VersionNumber.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/versioning/VersionNumber.java
index 228586411..55d0bc7b4 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/versioning/VersionNumber.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/versioning/VersionNumber.java
@@ -25,6 +25,7 @@ import java.util.*;
 /**
  * Copied from org.apache.maven.artifact.versioning.ComparableVersion
  * Apache License 2.0
+ * @see <a href="http://maven.apache.org/pom.html#Version_Order_Specification">Specification</a>
  */
 public class VersionNumber implements Comparable<VersionNumber> {
 
diff --git a/HMCLauncher/HMCL/main.cpp b/HMCLauncher/HMCL/main.cpp
index 61fd58e7a..905b31141 100644
--- a/HMCLauncher/HMCL/main.cpp
+++ b/HMCLauncher/HMCL/main.cpp
@@ -20,7 +20,7 @@ int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmd
 	if (ERROR_SUCCESS != MyGetModuleFileName(NULL, exeName))
 		return 1;
 
-
+	// TODO: check whether the bundled JRE is valid.
 	// First try the Java packaged together.
 	bool is64Bit = false;
 	GetArch(is64Bit); // if failed to determine architecture of operating system, consider 32-bit.