BAEL-885 - How to merge two Java streams? (#1986)

Use the java.util.stream.Stream interface as much as possible

libraries/src/test/java/com/baeldung/stream/JoolMergeStreamsTest.java

@@ -5,31 +5,35 @@ import org.junit.Assert;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static junit.framework.TestCase.assertEquals;
 
 public class JoolMergeStreamsTest {
     @Test
     public void givenTwoStreams_whenMergingStreams_thenResultingStreamContainsElementsFromBothStreams() {
-        Seq<Integer> seq1 = Seq.of(1, 3, 5);
+        Stream<Integer> seq1 = Stream.of(1, 3, 5);
-        Seq<Integer> seq2 = Seq.of(2, 4, 6);
+        Stream<Integer> seq2 = Stream.of(2, 4, 6);
 
-        Seq<Integer> resultingSeq = seq1.append(seq2);
+        Stream<Integer> resultingSeq = Seq.ofType(seq1, Integer.class)
+                                          .append(seq2);
 
         assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6),
-                     resultingSeq.toList());
+                     resultingSeq.collect(Collectors.toList()));
     }
 
     @Test
     public void givenThreeStreams_whenAppendingAndPrependingStreams_thenResultingStreamContainsElementsFromAllStreams() {
-        Seq<String> seq = Seq.of("foo", "bar");
+        Stream<String> seq = Stream.of("foo", "bar");
-        Seq<String> openingBracketSeq = Seq.of("[");
+        Stream<String> openingBracketSeq = Stream.of("[");
-        Seq<String> closingBracketSeq = Seq.of("]");
+        Stream<String> closingBracketSeq = Stream.of("]");
 
-        Seq<String> resultingStream = seq.append(closingBracketSeq)
+        Stream<String> resultingStream = Seq.ofType(seq, String.class)
-                                         .prepend(openingBracketSeq);
+                                            .append(closingBracketSeq)
+                                            .prepend(openingBracketSeq);
 
         Assert.assertEquals(Arrays.asList("[", "foo", "bar", "]"),
-                            resultingStream.toList());
+                            resultingStream.collect(Collectors.toList()));
     }
 }

libraries/src/test/java/com/baeldung/stream/StreamExMergeStreamsTest.java

@@ -4,6 +4,8 @@ import one.util.streamex.StreamEx;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static org.junit.Assert.assertEquals;
 
@@ -11,41 +13,43 @@ public class StreamExMergeStreamsTest {
 
     @Test
     public void givenTwoStreams_whenMergingStreams_thenResultingStreamContainsElementsFromBothStreams() {
-        StreamEx<Integer> stream1 = StreamEx.of(1, 3, 5);
+        Stream<Integer> stream1 = Stream.of(1, 3, 5);
-        StreamEx<Integer> stream2 = StreamEx.of(2, 4, 6);
+        Stream<Integer> stream2 = Stream.of(2, 4, 6);
 
-        StreamEx<Integer> resultingStream = stream1.append(stream2);
+        Stream<Integer> resultingStream = StreamEx.of(stream1).append(stream2);
 
         assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6),
-                     resultingStream.toList());
+                     resultingStream.collect(Collectors.toList()));
     }
 
     @Test
     public void givenFourStreams_whenMergingStreams_thenResultingStreamContainsElementsFromAllStreams() {
-        StreamEx<Integer> stream1 = StreamEx.of(1, 3, 5);
+        Stream<Integer> stream1 = Stream.of(1, 3, 5);
-        StreamEx<Integer> stream2 = StreamEx.of(2, 4, 6);
+        Stream<Integer> stream2 = Stream.of(2, 4, 6);
-        StreamEx<Integer> stream3 = StreamEx.of(18, 15, 36);
+        Stream<Integer> stream3 = Stream.of(18, 15, 36);
-        StreamEx<Integer> stream4 = StreamEx.of(99);
+        Stream<Integer> stream4 = Stream.of(99);
 
-        StreamEx<Integer> resultingStream = stream1.append(stream2)
+        Stream<Integer> resultingStream = StreamEx.of(stream1)
-                                                   .append(stream3)
+                                                  .append(stream2)
-                                                   .append(stream4);
+                                                  .append(stream3)
+                                                  .append(stream4);
 
         assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6, 18, 15, 36, 99),
-                     resultingStream.toList());
+                     resultingStream.collect(Collectors.toList()));
 
     }
 
     @Test
     public void givenThreeStreams_whenAppendingAndPrependingStreams_thenResultingStreamContainsElementsFromAllStreams() {
-        StreamEx<String> stream1 = StreamEx.of("foo", "bar");
+        Stream<String> stream1 = Stream.of("foo", "bar");
-        StreamEx<String> openingBracketStream = StreamEx.of("[");
+        Stream<String> openingBracketStream = Stream.of("[");
-        StreamEx<String> closingBracketStream = StreamEx.of("]");
+        Stream<String> closingBracketStream = Stream.of("]");
 
-        StreamEx<String> resultingStream = stream1.append(closingBracketStream)
+        Stream<String> resultingStream = StreamEx.of(stream1)
-                                                  .prepend(openingBracketStream);
+                                                 .append(closingBracketStream)
+                                                 .prepend(openingBracketStream);
 
         assertEquals(Arrays.asList("[", "foo", "bar", "]"),
-                     resultingStream.toList());
+                     resultingStream.collect(Collectors.toList()));
     }
 }