PluginINstaller: fix retrieving remote metadata

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

src/org/omegat/util/PluginInstaller.java

@@ -36,6 +36,7 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.Enumeration;
 import java.util.HashSet;
@@ -44,13 +45,13 @@
 import java.util.Scanner;
 import java.util.Set;
 import java.util.TreeMap;
-import java.util.TreeSet;
 import java.util.function.Predicate;
 import java.util.jar.Manifest;
 
 import javax.swing.JOptionPane;
 
 import org.apache.commons.io.FileUtils;
+
 import org.omegat.core.Core;
 import org.omegat.core.data.PluginInformation;
 import org.omegat.filters2.master.PluginUtils;
@@ -249,8 +250,8 @@ private static Map<String, PluginInformation> getInstalledPlugins() {
      * Download plugin list from github repository.
      * @return set of PluginInformation
      */
-    private static Set<PluginInformation> getPluginsList() {
-        Set<PluginInformation> pluginInfo = new TreeSet<>();
+    private static List<PluginInformation> getPluginsList() {
+        List<PluginInformation> pluginInfo = new ArrayList<>();
         String raw_value;
         try {
             raw_value = HttpConnectionUtils.getURL(new URL(LIST_URL));