How to zip two collections in Java? (#2176)

* How to zip two collections in Java?

How to zip two collections in Java? | http://jira.baeldung.com/browse/BAEL-780

* Updated pom to add jool dependency

* Added Unit Tests of Zip Collections

* Moved files to libraries folder

* Fixed Compilation Error

* Removed jool dependency as code has been moved to libraries

* Removed jool property attribute

core-java/pom.xml

@@ -417,4 +417,4 @@
         <maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
 
     </properties>
-</project>
+</project>

libraries/pom.xml

@@ -349,6 +349,12 @@
             <artifactId>java-lsh</artifactId>
             <version>${java-lsh.version}</version>
         </dependency>
+        <!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>21.0</version>
+        </dependency>
         <dependency>
             <groupId>au.com.dius</groupId>
             <artifactId>pact-jvm-consumer-junit_2.11</artifactId>

libraries/src/main/java/com/baeldung/zip/ZipCollectionExample.java

@@ -0,0 +1,40 @@
+package com.baeldung.zip;
+
+import com.google.common.collect.Streams;
+import org.jooq.lambda.Seq;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.IntStream;
+
+public class ZipCollectionExample {
+    static List<String> names = Arrays.asList("John", "Jane", "Jack", "Dennis");
+
+    static List<Integer> ages = Arrays.asList(24, 25, 27);
+
+    public static void main(String[] args) {
+        //      Using Streams API from Guava 21
+        Streams
+          .zip(names.stream(), ages.stream(), (name, age) -> name + ":" + age)
+          .forEach(System.out::println);
+
+        //        Using native Java 8 Int Stream
+        IntStream
+          .range(0, Math.min(names.size(), ages.size()))
+          .mapToObj(i -> names.get(i) + ":" + ages.get(i))
+          .forEach(System.out::println);
+
+        //      Using jOOL
+        Seq
+          .of("John", "Jane", "Dennis")
+          .zip(Seq.of(24, 25, 27));
+
+        Seq
+          .of("John", "Jane", "Dennis")
+          .zip(Seq.of(24, 25, 27), (x, y) -> x + ":" + y);
+
+        Seq
+          .of("a", "b", "c")
+          .zipWithIndex();
+    }
+}

libraries/src/test/java/com/baeldung/zip/ZipCollectionTest.java

@@ -0,0 +1,85 @@
+package com.baeldung.zip;
+
+import com.google.common.collect.Streams;
+import org.jooq.lambda.Seq;
+import org.jooq.lambda.tuple.Tuple2;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+
+public class ZipCollectionTest {
+
+    List<String> names;
+    List<Integer> ages;
+    List<String> expectedOutput;
+
+    @Before
+    public void setUp() throws Exception {
+        names = Arrays.asList("John", "Jane", "Jack", "Dennis");
+        ages = Arrays.asList(24, 25, 27);
+        expectedOutput = Arrays.asList("John:24", "Jane:25", "Jack:27");
+    }
+
+    @Test
+    public void zipCollectionUsingGuava21() {
+        List<String> output = Streams
+          .zip(names.stream(), ages.stream(), (name, age) -> name + ":" + age)
+          .collect(Collectors.toList());
+
+        assertEquals(output, expectedOutput);
+    }
+
+    @Test
+    public void zipCollectionUsingIntStream() {
+        List<String> output = IntStream
+          .range(0, Math.min(names.size(), ages.size()))
+          .mapToObj(i -> names.get(i) + ":" + ages.get(i))
+          .collect(Collectors.toList());
+
+        assertEquals(output, expectedOutput);
+    }
+
+    @Test
+    public void zipCollectionUsingJool() {
+        Seq<String> output = Seq
+          .of("John", "Jane", "Jack")
+          .zip(Seq.of(24, 25, 27), (x, y) -> x + ":" + y);
+
+        assertEquals(output.toList(), expectedOutput);
+    }
+
+    @Test
+    public void zipCollectionUsingJoolTuple() {
+        Seq<Tuple2<String, Integer>> output = Seq
+          .of("John", "Jane", "Dennis")
+          .zip(Seq.of(24, 25, 27));
+
+        Tuple2<String, Integer> element1 = new Tuple2<String, Integer>("John", 24);
+        Tuple2<String, Integer> element2 = new Tuple2<String, Integer>("Jane", 25);
+        Tuple2<String, Integer> element3 = new Tuple2<String, Integer>("Dennis", 27);
+
+        List<Tuple2> expectedOutput = Arrays.asList(element1, element2, element3);
+        assertEquals(output.collect(Collectors.toList()), expectedOutput);
+    }
+
+    @Test
+    public void zipCollectionUsingJoolWithIndex() {
+        Seq<Tuple2<String, Long>> output = Seq
+          .of("John", "Jane", "Dennis")
+          .zipWithIndex();
+
+        Tuple2<String, Long> element1 = new Tuple2<>("John", 0L);
+        Tuple2<String, Long> element2 = new Tuple2<>("Jane", 1L);
+        Tuple2<String, Long> element3 = new Tuple2<>("Dennis", 2L);
+
+        List<Tuple2> expectedOutput = Arrays.asList(element1, element2, element3);
+        assertEquals(output.collect(Collectors.toList()), expectedOutput);
+    }
+
+}