This PR is related to BAEL-7174 (#15681)

* This PR is related to BAEL-7174

This PR aims to add a new test class "CheckIfStringContainsInvalidEncodedCharactersUnitTest".

* Update CheckIfStringContainsInvalidEncodedCharactersUnitTest.java

Updating if-else with ternary operator

core-java-modules/core-java-string-operations-7/src/test/java/com/baeldung/checkifstringcontainsinvalidcharacters/CheckIfStringContainsInvalidEncodedCharactersUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.checkifstringcontainsinvalidcharacters;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.*;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class CheckIfStringContainsInvalidEncodedCharactersUnitTest {
+
+    public String input = "HÆllo, World!";
+
+    @Test
+    public void givenInputString_whenUsingRegexPattern_thenFindIfInvalidCharacters() {
+        String regexPattern = "[^\\x00-\\x7F]+";
+        Pattern pattern = Pattern.compile(regexPattern);
+        Matcher matcher = pattern.matcher(input);
+        assertTrue(matcher.find() ? true : false);
+    }
+
+    @Test
+    public void givenInputString_whenUsingStringEncoding_thenFindIfInvalidCharacters() {
+        byte[] bytes = input.getBytes(StandardCharsets.UTF_8);
+        boolean found = false;
+        for (byte b : bytes) {
+            found = (b & 0xFF) > 127 ? true : found;
+        }
+        assertTrue(found ? true : false);
+    }
+}