BAEL-6816-create-stream-regex-matches (#14731)

* BAEL-6816-create-stream-regex-matches

* add unit test

---------

Co-authored-by: tienvn <tienvn@>

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/regexmatches/StreamFromRegexUtil.java

@@ -0,0 +1,16 @@
+package com.baeldung.streams.regexmatches;
+
+import java.util.regex.MatchResult;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Stream;
+
+public class StreamFromRegexUtil {
+
+    public static Stream<String> getStream(String input, String regex) {
+        Pattern pattern = Pattern.compile(regex);
+        Matcher matcher = pattern.matcher(input);
+        return matcher.results().map(MatchResult::group);
+    }
+
+}

core-java-modules/core-java-9-streams/src/test/java/com/baeldung/streams/regexmatches/StreamFromRegexUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.streams.regexmatches;
+
+import org.junit.Test;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static java.util.Arrays.asList;
+import static org.junit.Assert.assertEquals;
+
+public class StreamFromRegexUnitTest {
+
+    @Test
+    public void whenInputStringIncludeLettersAndNumbersAndRegex_ThenReturnStreamOfNumbers() {
+        List<String> result = StreamFromRegexUtil.getStream("There are 3 apples and 2 bananas on the table.", "\\d+")
+                .collect(Collectors.toList());
+        assertEquals(asList("3", "2"), result);
+    }
+
+    @Test
+    public void whenInputStringsAndRegex_ThenReturnStreamOfJavaWords() {
+        List<String> result = StreamFromRegexUtil.getStream("sample sentence with some words Java Java", "\\bJava\\b")
+                .collect(Collectors.toList());
+        assertEquals(asList("Java", "Java"), result);
+    }
+
+}