BAEL-4560 Add various patterns for adding iteration counter to loops/streams (eugenp#10266)

ashleyfrieze · web-flow · commit baa1609267aa · 2020-11-23T18:13:16.000Z
* Add various patterns for adding iteration counter to loops/streams

* Add various patterns for adding iteration counter to loops/streams
diff --git a/core-java-modules/core-java-lang-3/src/main/java/com/baeldung/iterationcounter/IterationCounter.java b/core-java-modules/core-java-lang-3/src/main/java/com/baeldung/iterationcounter/IterationCounter.java
@@ -0,0 +1,68 @@
+package com.baeldung.iterationcounter;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+
+public class IterationCounter {
+    public static final List<String> IMDB_TOP_MOVIES = Arrays.asList("The Shawshank Redemption",
+      "The Godfather", "The Godfather II", "The Dark Knight");
+
+    public static List<String> getRankingsWithForLoop(List<String> movies) {
+        List<String> rankings = new ArrayList<>();
+        for (int i = 0; i < movies.size(); i++) {
+            String ranking = (i + 1) + ": " + movies.get(i);
+            rankings.add(ranking);
+        }
+        return rankings;
+    }
+
+    public static List<String> getRankingsWithForEachLoop(List<String> movies) {
+        List<String> rankings = new ArrayList<>();
+        int i = 0;
+        for (String movie : movies) {
+            String ranking = (i + 1) + ": " + movies.get(i);
+            rankings.add(ranking);
+
+            i++;
+        }
+        return rankings;
+    }
+
+    public static List<String> getRankingsWithFunctionalForEachLoop(List<String> movies) {
+        List<String> rankings = new ArrayList<>();
+        forEachWithCounter(movies, (i, movie) -> {
+            String ranking = (i + 1) + ": " + movie;
+            rankings.add(ranking);
+        });
+
+        return rankings;
+    }
+
+    public static <T> void forEachWithCounter(Iterable<T> source, BiConsumer<Integer, T> consumer) {
+        int i = 0;
+        for (T item : source) {
+            consumer.accept(i, item);
+            i++;
+        }
+    }
+
+    public static List<String> getRankingsWithStream(Stream<String> movies) {
+        List<String> rankings = new ArrayList<>();
+        movies.forEach(withCounter((i, movie) -> {
+            String ranking = (i + 1) + ": " + movie;
+            rankings.add(ranking);
+        }));
+
+        return rankings;
+    }
+
+    public static <T> Consumer<T> withCounter(BiConsumer<Integer, T> consumer) {
+        AtomicInteger counter = new AtomicInteger(0);
+        return item -> consumer.accept(counter.getAndIncrement(), item);
+    }
+}
diff --git a/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/iterationcounter/IterationCounterUnitTest.java b/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/iterationcounter/IterationCounterUnitTest.java
@@ -0,0 +1,36 @@
+package com.baeldung.iterationcounter;
+
+import org.junit.Test;
+
+import static com.baeldung.iterationcounter.IterationCounter.*;
+import static org.assertj.core.api.Assertions.*;
+
+public class IterationCounterUnitTest {
+    @Test
+    public void givenRankings_whenCalculateWithForLoop_thenRankingsCorrect() {
+        assertThat(getRankingsWithForLoop(IMDB_TOP_MOVIES))
+          .containsExactly("1: The Shawshank Redemption",
+            "2: The Godfather", "3: The Godfather II", "4: The Dark Knight");
+    }
+
+    @Test
+    public void givenRankings_whenCalculateWithForEachLoop_thenRankingsCorrect() {
+        assertThat(getRankingsWithForEachLoop(IMDB_TOP_MOVIES))
+          .containsExactly("1: The Shawshank Redemption",
+            "2: The Godfather", "3: The Godfather II", "4: The Dark Knight");
+    }
+
+    @Test
+    public void givenRankings_whenCalculateWithFunctionalForEach_thenRankingsCorrect() {
+        assertThat(getRankingsWithFunctionalForEachLoop(IMDB_TOP_MOVIES))
+          .containsExactly("1: The Shawshank Redemption",
+            "2: The Godfather", "3: The Godfather II", "4: The Dark Knight");
+    }
+
+    @Test
+    public void givenRankings_whenCalculateWithStream_thenRankingsCorrect() {
+        assertThat(getRankingsWithStream(IMDB_TOP_MOVIES.stream()))
+          .containsExactly("1: The Shawshank Redemption",
+            "2: The Godfather", "3: The Godfather II", "4: The Dark Knight");
+    }
+}
