implement method to shuffle password characters

src/main/java/PasswordGenerator.java

@@ -6,6 +6,7 @@ public class PasswordGenerator {
     final String uppercaseCharacters = "ABCDEFGHJKMNPQRSTUVWXYZ";
     final String digits = "0123456789";
     final String specialCharacters = ".!?=@#$()%^&/*_-+";
+    final SecureRandom rand = new SecureRandom();
 
     private int length = 12;
     private boolean useUppercase = true;
@@ -17,7 +18,6 @@ public class PasswordGenerator {
 
     public String generateRandomPassword() {
         StringBuilder generatedPassword = new StringBuilder();
-        SecureRandom rand = new SecureRandom();
         String characterPool = "";
 
         if (isUseLowercase()) {
@@ -55,6 +55,19 @@ public class PasswordGenerator {
         return generatedPassword.toString();
     }
 
+    public String shufflePassword(String password) {
+        StringBuilder shuffledPassword = new StringBuilder();
+        StringBuilder passwordCopy = new StringBuilder(password);
+
+        while (passwordCopy.length() != 0) {
+            int index = rand.nextInt(passwordCopy.length());
+            char c = passwordCopy.charAt(index);
+            shuffledPassword.append(c);
+            passwordCopy.deleteCharAt(index);
+        }
+        return shuffledPassword.toString();
+    }
+
     public boolean isUseUppercase() {
         return useUppercase;
     }

src/test/java/PasswordGeneratorTest.java

@@ -62,4 +62,11 @@ class PasswordGeneratorTest {
         PasswordValidator passwordValidator = new PasswordValidator();
         assertTrue(passwordValidator.validate(passwordGenerator.generateRandomPassword()));
     }
+
+    @Test
+    void testShufflePassword() {
+        String testInput = "ABcdefgh123";
+        assertNotEquals(passwordGenerator.shufflePassword(testInput), testInput);
+        assertEquals(passwordGenerator.shufflePassword(testInput).length(), testInput.length());
+    }
 }