Use List.sort instead of Collections.sort

compiler/frontend/src/org/jetbrains/kotlin/checkers/CheckerTestUtil.java

@@ -604,7 +604,7 @@ public class CheckerTestUtil {
             diagnosticDescriptors.add(
                     new DiagnosticDescriptor(range.getStartOffset(), range.getEndOffset(), diagnosticsGroupedByRanges.get(range)));
         }
-        Collections.sort(diagnosticDescriptors, (d1, d2) -> {
+        diagnosticDescriptors.sort((d1, d2) -> {
             // Start early -- go first; start at the same offset, the one who end later is the outer, i.e. goes first
             return (d1.start != d2.start) ? d1.start - d2.start : d2.end - d1.end;
         });

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/DiagnosticUtils.java

@@ -160,7 +160,8 @@ public class DiagnosticUtils {
 
     @NotNull
     public static List<Diagnostic> sortedDiagnostics(@NotNull Collection<Diagnostic> diagnostics) {
-        Comparator<Diagnostic> diagnosticComparator = (d1, d2) -> {
+        List<Diagnostic> result = Lists.newArrayList(diagnostics);
+        result.sort((d1, d2) -> {
             String path1 = d1.getPsiFile().getViewProvider().getVirtualFile().getPath();
             String path2 = d2.getPsiFile().getViewProvider().getVirtualFile().getPath();
             if (!path1.equals(path2)) return path1.compareTo(path2);
@@ -173,9 +174,7 @@ public class DiagnosticUtils {
             }
 
             return d1.getFactory().getName().compareTo(d2.getFactory().getName());
-        };
-        List<Diagnostic> result = Lists.newArrayList(diagnostics);
-        Collections.sort(result, diagnosticComparator);
+        });
         return result;
     }
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintsUtil.java

@@ -123,7 +123,7 @@ public class ConstraintsUtil {
                 interestingMethods.add(method);
             }
         }
-        Collections.sort(interestingMethods, Comparator.comparing(Method::getName));
+        interestingMethods.sort(Comparator.comparing(Method::getName));
         for (Iterator<Method> iterator = interestingMethods.iterator(); iterator.hasNext(); ) {
             Method method = iterator.next();
             try {