IDEA-CR-16002 sort settings dropdowns sdks together only by the same sdk comparator object instance; @NotNull annotating; make SdkComparator not lazy initializable singleton

java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/JdkComboBox.java

@@ -305,19 +305,41 @@ public class JdkComboBox extends ComboBoxWithWidePopup {
       }
     }
 
+    private static class MyComparatorWrapper {
+      @NotNull
+      private final Comparator<Sdk> myComparator;
+
+      MyComparatorWrapper(@NotNull final Comparator<Sdk> comparator) {
+        myComparator = comparator;
+      }
+
+      @Override
+      public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        return myComparator == ((MyComparatorWrapper)o).myComparator;
+      }
+
+      @Override
+      public int hashCode() {
+        return myComparator.hashCode();
+      }
+    }
+
     @NotNull
     private static Sdk[] sortSdks(@NotNull final Sdk[] sdks) {
-      MultiMap<Comparator<Sdk>, Sdk> comparatorToSdkMap = new MultiMap<>();
+      MultiMap<MyComparatorWrapper, Sdk> comparatorToSdkMap = new MultiMap<>();
       for (Sdk sdk : sdks) {
         final SdkTypeId sdkType = sdk.getSdkType();
         if (sdkType instanceof SdkType) {
-          comparatorToSdkMap.putValue(((SdkType)sdkType).getComparator(), sdk);
+          comparatorToSdkMap.putValue(new MyComparatorWrapper(((SdkType)sdkType).getComparator()), sdk);
         } else {
-          comparatorToSdkMap.putValue(SdkType.ALPHABETICAL_COMPARATOR, sdk);
+          comparatorToSdkMap.putValue(new MyComparatorWrapper(SdkType.ALPHABETICAL_COMPARATOR), sdk);
         }
       }
 
-      return comparatorToSdkMap.entrySet().stream().flatMap(entry -> entry.getValue().stream().sorted(entry.getKey()))
+      return comparatorToSdkMap.entrySet().stream().flatMap(entry -> entry.getValue().stream().sorted(entry.getKey().myComparator))
         .toArray(size -> new Sdk[size]);
     }
 

platform/lang-api/src/com/intellij/openapi/projectRoots/SdkType.java

@@ -94,9 +94,10 @@ public abstract class SdkType implements SdkTypeId {
 
   /**
    * Returns comparator which is used to order sdks in project or module settings combo boxes.
-   * If different sdk types return the same comparator object then they are sorted together.
+   * If different sdk types return the same comparator instance then they are sorted together.
    */
 
+  @NotNull
   public Comparator<Sdk> getComparator() {
     return ALPHABETICAL_COMPARATOR;
   }