IDEA-170626 Suggest to use Stream.peek instead of Stream.map if the lambda parameter is not reassigned during the operation.

java/java-tests/testData/inspection/streamApiCallChains/afterMapToPeek.java

@@ -0,0 +1,14 @@
+// "Replace with 'peek'" "true"
+
+import java.util.List;
+
+public class Main {
+  void test(List<String> list) {
+      // hello
+/* in return */
+      long count = list.stream()
+      .peek(System.out::println)
+      .count();
+    System.out.println(count);
+  }
+}

java/java-tests/testData/inspection/streamApiCallChains/afterMapToPeekPrimitive.java

@@ -0,0 +1,15 @@
+// "Replace with 'peek'" "true"
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.IntStream;
+
+public class Main {
+  void test() {
+    AtomicInteger counter = new AtomicInteger();
+    int[] ints = IntStream.range(0, 100)
+      .filter(x -> x % 3 == 0)
+      .peek((x -> counter.incrementAndGet()))
+      .toArray();
+    System.out.println(counter.get());
+  }
+}

java/java-tests/testData/inspection/streamApiCallChains/beforeMapToPeek.java

@@ -0,0 +1,16 @@
+// "Replace with 'peek'" "true"
+
+import java.util.List;
+
+public class Main {
+  void test(List<String> list) {
+    long count = list.stream()
+      .ma<caret>p(e -> {
+        System.out.println(e);
+        // hello
+        return /* in return */ e;
+      })
+      .count();
+    System.out.println(count);
+  }
+}

java/java-tests/testData/inspection/streamApiCallChains/beforeMapToPeekPrimitive.java

@@ -0,0 +1,18 @@
+// "Replace with 'peek'" "true"
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.IntStream;
+
+public class Main {
+  void test() {
+    AtomicInteger counter = new AtomicInteger();
+    int[] ints = IntStream.range(0, 100)
+      .filter(x -> x % 3 == 0)
+      .m<caret>ap((x -> {
+        counter.incrementAndGet();
+        return x;
+      }))
+      .toArray();
+    System.out.println(counter.get());
+  }
+}

java/java-tests/testData/inspection/streamApiCallChains/beforeMapToPeekWritten.java

@@ -0,0 +1,16 @@
+// "Replace with 'peek'" "false"
+
+import java.util.stream.IntStream;
+
+public class Main {
+  void test() {
+    int[] ints = IntStream.range(0, 100)
+      .filter(x -> x % 3 == 0)
+      .m<caret>ap(x -> {
+        x++;
+        return x;
+      })
+      .toArray();
+    System.out.println(ints.length);
+  }
+}