BAEL-4665: add text blocks to multiline strings test (#10777)

* BAEL-4665: add text blocks to multiline strings test

* BAEL-4665: move core-java-strings to jdk9 profile

core-java-modules/core-java-strings/pom.xml

@@ -57,6 +57,7 @@
     <properties>
         <assertj.version>3.6.1</assertj.version>
         <icu4j.version>61.1</icu4j.version>
+        <maven.compiler.release>15</maven.compiler.release>
     </properties>
 
 </project>

core-java-modules/core-java-strings/src/main/java/com/baeldung/multiline/MultiLineString.java

@@ -64,4 +64,11 @@ public class MultiLineString {
         return new String(Files.readAllBytes(Paths.get("src/main/resources/stephenking.txt")));
     }
 
+    public String textBlocks() {
+        return """
+            Get busy living
+            or
+            get busy dying.
+            --Stephen King""";
+    }
 }

core-java-modules/core-java-strings/src/test/java/com/baeldung/multiline/MultiLineStringUnitTest.java

@@ -16,6 +16,7 @@ public class MultiLineStringUnitTest {
         assertEquals(ms.stringJoin(), ms.stringBuilder());
         assertEquals(ms.stringBuilder(), ms.guavaJoiner());
         assertEquals(ms.guavaJoiner(), ms.loadFromFile());
+        assertEquals(ms.loadFromFile(), ms.textBlocks());
     }
     
 }