StreamToLoopInspection: support some simple StreamEx scenarios; support Java 9 takeWhile/dropWhile

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamToLoop/beforeTakeDrop.java

@@ -0,0 +1,29 @@
+// "Replace Stream API chain with loop" "true"
+
+import java.util.List;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Test {
+  // Mock Java 9 methods with inheritor
+  interface MyStream<T> extends Stream<T> {
+    <R> MyStream<R> flatMap(Function<? super T, ? extends Stream<? extends R>> mapper);
+
+    MyStream<T> takeWhile(Predicate<? super T> predicate);
+
+    MyStream<T> dropWhile(Predicate<? super T> predicate);
+
+    static <T> MyStream<T> of(List<T> list) {
+      return null;
+    }
+  }
+
+  public static void test(List<String> data) {
+    List<String> xyz = MyStream.of(data)
+      .flatMap(s -> Stream.of(s, s + s)).takeWhile(s -> !s.isEmpty())
+      .dropWhile(s -> s.length() < 3).col<caret>lect(Collectors.toList());
+    System.out.println(xyz);
+  }
+}