feat: Add method RemoveDuplicatesCharacters from string

JavaDsaWithTest/src/main/java/org/practice/dsa/strings/RemoveDuplicatesCharacters.java

@@ -0,0 +1,45 @@
+package org.practice.dsa.strings;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class RemoveDuplicatesCharacters {
+    public static void main(String[] args) {
+        System.out.println(removeDuplicates("Vishwajeet"));
+        System.out.println(removeDuplicatesForLoop("principle"));
+    }
+
+    public static String removeDuplicates(String str) {
+        Set<Character> set = new HashSet<>();
+        StringBuilder builder = new StringBuilder();
+
+        for (char ch: str.toCharArray()) {
+            if (set.add(ch)) {
+                builder.append(ch);
+            }
+        }
+        return builder.toString();
+    }
+
+    // using for loops
+    public static String removeDuplicatesForLoop(String str) {
+        StringBuilder stringBuilder = new StringBuilder();
+
+        for (int i = 0; i < str.length(); i++) {
+            char current = str.charAt(i);
+
+            boolean isDuplicate = false;
+
+            for (int j = 0; j < stringBuilder.length(); j++) {
+                if (stringBuilder.charAt(j) == current) {
+                    isDuplicate = true;
+                    break;
+                }
+            }
+            if (!isDuplicate) {
+                stringBuilder.append(current);
+            }
+        }
+        return stringBuilder.toString();
+    }
+}