IDEA-166211 Convert for-loop with Collections.addAll inside into Java 8's stream API calls chain

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterCollectionsAddAllArray.java

@@ -0,0 +1,8 @@
+// "Replace with toArray" "true"
+import java.util.*;
+
+public class Test {
+  Object[] test(List<String[]> list) {
+      return list.stream().filter(Objects::nonNull).flatMap(Arrays::stream).sorted().toArray();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterCollectionsAddAllVarArg.java

@@ -0,0 +1,13 @@
+// "Replace with toArray" "true"
+import java.util.*;
+import java.util.stream.Stream;
+
+public class Test {
+  Object[] test(List<String> list) {
+      return list.stream().filter(Objects::nonNull).flatMap(str -> Stream.of(str, str + str)).sorted().toArray();
+  }
+
+  public static void main(String[] args) {
+    System.out.println(Arrays.toString(new Test().test(Arrays.asList("a", "b", "ba", "x", null, "c"))));
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeCollectionsAddAllArray.java

@@ -0,0 +1,15 @@
+// "Replace with toArray" "true"
+import java.util.*;
+
+public class Test {
+  Object[] test(List<String[]> list) {
+    List<Object> result = new LinkedList<>();
+    for(String[] str : li<caret>st) {
+      if(str != null) {
+        Collections.addAll(result, str);
+      }
+    }
+    result.sort(null);
+    return result.toArray();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeCollectionsAddAllVarArg.java

@@ -0,0 +1,19 @@
+// "Replace with toArray" "true"
+import java.util.*;
+
+public class Test {
+  Object[] test(List<String> list) {
+    List<Object> result = new LinkedList<>();
+    for(String str : lis<caret>t) {
+      if(str != null) {
+        Collections.addAll(result, str, str+str);
+      }
+    }
+    result.sort(null);
+    return result.toArray();
+  }
+
+  public static void main(String[] args) {
+    System.out.println(Arrays.toString(new Test().test(Arrays.asList("a", "b", "ba", "x", null, "c"))));
+  }
+}