issue # 랜덤 코드 생성기 구현

src/main/java/com/baekyangdan/scheduler/utils/generator/RandomCodeGenerator.java

@@ -0,0 +1,35 @@
+package com.baekyangdan.scheduler.utils.generator;
+
+import java.security.SecureRandom;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class RandomCodeGenerator {
+    private static final String DIGITS = "0123456789";
+    private static final SecureRandom random = new SecureRandom();
+
+    public static String generateRandomCode(int length) {
+        List<Character> codeCharacters = ArrayList<>(length);
+
+        for (int i = 0; i < length; i++) {
+            codeCharacters.add(randomChar());
+        }
+
+        Collections.shuffle(codeCharacters, random);
+
+        StringBuilder sb = new StringBuilder(length);
+
+        for (char c : codeCharacters) {
+            sb.append(c);
+        }
+
+        return sb.toString();
+    }
+
+    private static char randomChar() {
+        int idx = random.nextInt(DIGITS.length());
+        return DIGITS.charAt(idx);
+    }
+}