diff --git a/contains-duplicate/TonyKim9401.java b/contains-duplicate/TonyKim9401.java
new file mode 100644
index 000000000..ef9037c49
--- /dev/null
+++ b/contains-duplicate/TonyKim9401.java
@@ -0,0 +1,17 @@
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        // HashSet  O(n)
+        /*
+        Set<Integer> set = new HashSet();
+        for (int num : nums) set.add(num);
+        return set.size() != nums.length;
+        */
+
+        // dupl value O(n log n)
+        Arrays.sort(nums);
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (nums[i] == nums[i + 1]) return true;
+        }
+        return false;
+    }
+}
\ No newline at end of file