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

* Add various patterns for adding iteration counter to loops/streams

* Add various patterns for adding iteration counter to loops/streams
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ashleyfrieze 2020-11-23 18:13:16 +00:00 committed by GitHub
parent 02a3978fae
commit c61ed5f8b0
2 changed files with 104 additions and 0 deletions
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68
core-java-modules/core-java-lang-3/src/main/java/com/baeldung/iterationcounter/IterationCounter.java Normal file
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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);
}
}

36
core-java-modules/core-java-lang-3/src/test/java/com/baeldung/iterationcounter/IterationCounterUnitTest.java Normal file
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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");
}
}