diff --git a/core-java-modules/core-java-string-operations-6/src/main/java/com/baeldung/uniquecharcheck/UniqueCharChecker.java b/core-java-modules/core-java-string-operations-6/src/main/java/com/baeldung/uniquecharcheck/UniqueCharChecker.java
new file mode 100644
index 0000000000..365307708c
--- /dev/null
+++ b/core-java-modules/core-java-string-operations-6/src/main/java/com/baeldung/uniquecharcheck/UniqueCharChecker.java
@@ -0,0 +1,60 @@
+package com.baeldung.uniquecharcheck;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+public class UniqueCharChecker {
+
+    public static boolean checkV1(String str) {
+        char[] chars = str.toUpperCase().toCharArray();
+        for (int i = 0; i < chars.length; i++) {
+            for (int j = i + 1; j < chars.length; j++) {
+                if(chars[i] == chars[j]) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    public static boolean checkV2(String str) {
+        char[] chars = str.toUpperCase().toCharArray();
+        Arrays.sort(chars);
+        for (int i = 0; i < chars.length - 1; i++) {
+            if(chars[i] == chars[i+1]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public static boolean checkV3(String str) {
+        char[] chars = str.toUpperCase().toCharArray();
+        Set <Character> set = new HashSet <>();
+        for (char c: chars) {
+            set.add(c);
+        }
+        return set.size() == str.length();
+    }
+
+    public static boolean checkV4(String str) {
+        boolean isUnique = str.toUpperCase().chars()
+                .mapToObj(c -> (char)c)
+                .collect(Collectors.toSet())
+                .size() == str.length();
+        return isUnique;
+    }
+
+    public static boolean checkV5(String str) {
+        for (int i = 0; i < str.length(); i++) {
+            String curChar = String.valueOf(str.charAt(i));
+            String remainingStr = str.substring(i+1);
+            if(StringUtils.containsIgnoreCase(remainingStr, curChar)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
diff --git a/core-java-modules/core-java-string-operations-6/src/test/java/com/baeldung/uniquecharcheck/UniqueCharCheckerUnitTest.java b/core-java-modules/core-java-string-operations-6/src/test/java/com/baeldung/uniquecharcheck/UniqueCharCheckerUnitTest.java
new file mode 100644
index 0000000000..938787662f
--- /dev/null
+++ b/core-java-modules/core-java-string-operations-6/src/test/java/com/baeldung/uniquecharcheck/UniqueCharCheckerUnitTest.java
@@ -0,0 +1,92 @@
+package com.baeldung.uniquecharcheck;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+
+public class UniqueCharCheckerUnitTest {
+
+    @Test
+    public void givenMethCheck1_whenUnique_returnTrue() {
+        String[] sampleStrings = new String[]{"Justfewdi123", "$%&Hibusc", "Hibusc%$#", "მშვნიერ"};
+        final String MSG = "Duplicate found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertTrue(MSG + " in " + sampleStr, UniqueCharChecker.checkV1(sampleStr)));
+    }
+    @Test
+    public void givenMethCheck2_whenUnique_returnTrue() {
+        String[] sampleStrings = new String[]{"Justfewdi123", "$%&Hibusc", "Hibusc%$#", "მშვნიერ"};
+        final String MSG = "Duplicate found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertTrue(MSG + " in " + sampleStr, UniqueCharChecker.checkV2(sampleStr)));
+    }
+
+    @Test
+    public void givenMethCheck3_whenUnique_returnTrue() {
+        String[] sampleStrings = new String[]{"Justfewdi123", "$%&Hibusc", "Hibusc%$#", "მშვნიერ"};
+        final String MSG = "Duplicate found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertTrue(MSG + " in " + sampleStr, UniqueCharChecker.checkV3(sampleStr)));
+    }
+
+    @Test
+    public void givenMethCheck4_whenUnique_returnTrue() {
+        String[] sampleStrings = new String[]{"Justfewdi123", "$%&Hibusc", "Hibusc%$#", "მშვნიერ"};
+        final String MSG = "Duplicate found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertTrue(MSG + " in " + sampleStr, UniqueCharChecker.checkV1(sampleStr)));
+    }
+    @Test
+    public void givenMethCheck5_whenUnique_returnTrue() {
+        String[] sampleStrings = new String[]{"Justfewdi123", "$%&Hibusc", "Hibusc%$#", "მშვნიერ"};
+        final String MSG = "Duplicate found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertTrue(MSG + " in " + sampleStr, UniqueCharChecker.checkV5(sampleStr)));
+    }
+
+    @Test
+    public void givenMethCheck1_whenNotUnique_returnFalse() {
+        String[] sampleStrings = new String[]{"Justfewdif123", "$%&Hibushc", "Hibusuc%$#", "Hi%busc%$#", "მშვენიერი"};
+        final String MSG = "Duplicate not found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertFalse(MSG + " in " + sampleStr, UniqueCharChecker.checkV1(sampleStr)));
+    }
+
+    @Test
+    public void givenMethCheck2_whenNotUnique_returnFalse() {
+        String[] sampleStrings = new String[]{"Justfewdif123", "$%&Hibushc", "Hibusuc%$#", "Hi%busc%$#", "მშვენიერი"};
+        final String MSG = "Duplicate not found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertFalse(MSG + " in " + sampleStr, UniqueCharChecker.checkV2(sampleStr)));
+
+    }
+
+    @Test
+    public void givenMethCheck3_whenNotUnique_returnFalse() {
+        String[] sampleStrings = new String[]{"Justfewdif123", "$%&Hibushc", "Hibusuc%$#", "Hi%busc%$#", "მშვენიერი"};
+        final String MSG = "Duplicate not found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertFalse(MSG + " in " + sampleStr, UniqueCharChecker.checkV3(sampleStr)));
+    }
+
+    @Test
+    public void givenMethCheck4_whenNotUnique_returnFalse() {
+        String[] sampleStrings = new String[]{"Justfewdif123", "$%&Hibushc", "Hibusuc%$#", "Hi%busc%$#", "მშვენიერი"};
+        final String MSG = "Duplicate not found";
+        Arrays.stream(sampleStrings)
+                .forEach(sampleStr -> assertFalse(MSG + " in " + sampleStr, UniqueCharChecker.checkV4(sampleStr)));
+    }
+
+@Test
+public void givenMethCheck5_whenNotUnique_returnFalse() {
+    String[] sampleStrings = new String[]{"Justfewdif123", "$%&Hibushc", "Hibusuc%$#", "Hi%busc%$#", "მშვენიერი"};
+    final String MSG = "Duplicate not found";
+    Arrays.stream(sampleStrings)
+            .forEach(sampleStr -> assertFalse(MSG + " in " + sampleStr, UniqueCharChecker.checkV5(sampleStr)));
+}
+
+}