StreamToLoopInspection: added ExplicitCollectTerminalOperation; StreamVariable simplified; guard checks added (IDEA-CR-15249)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamToLoop/afterCollect3.java

@@ -0,0 +1,22 @@
+// "Replace Stream API chain with loop" "true"
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+public class Main {
+  private static void test(List<String> list) {
+      StringBuilder sb = new StringBuilder();
+      for (String str : list) {
+          if (Objects.nonNull(str)) {
+              sb.append(str);
+          }
+      }
+      String result = sb.toString();
+    System.out.println(result);
+  }
+
+  public static void main(String[] args) {
+    test(Arrays.asList("aa", "bbb", "c", null, "dd"));
+  }
+}