adding missing file

Author: lemire

fastfilter/src/main/java/org/fastfilter/xor/Deduplicator.java

@@ -0,0 +1,27 @@
+package org.fastfilter.xor;
+
+import java.util.Arrays;
+
+public class Deduplicator {
+
+    /**
+     * Sorts the keys array and removes duplicates in place.
+     * Returns the new length of the array (number of unique elements).
+     *
+     * @param keys the array of keys to deduplicate
+     * @param length the current length of the array
+     * @return the new length after removing duplicates
+     */
+    public static int sortAndRemoveDup(long[] keys, int length) {
+        Arrays.sort(keys, 0, length);
+        int j = 1;
+        for (int i = 1; i < length; i++) {
+            if (keys[i] != keys[i - 1]) {
+                keys[j] = keys[i];
+                j++;
+            }
+        }
+        return j;
+    }
+
+}