diff --git a/paimon-common/src/main/java/org/apache/paimon/fileindex/bloomfilter/BloomFilterFileIndex.java b/paimon-common/src/main/java/org/apache/paimon/fileindex/bloomfilter/BloomFilterFileIndex.java
index 46fcde0f1f41..c0486d535895 100644
--- a/paimon-common/src/main/java/org/apache/paimon/fileindex/bloomfilter/BloomFilterFileIndex.java
+++ b/paimon-common/src/main/java/org/apache/paimon/fileindex/bloomfilter/BloomFilterFileIndex.java
@@ -26,9 +26,18 @@
 import org.apache.paimon.types.DataType;
 import org.apache.paimon.utils.BloomFilter64;
 
+import org.apache.hadoop.util.bloom.HashFunction;
+
 import java.util.BitSet;
 
-/** Bloom filter for file index. */
+/**
+ * Bloom filter for file index.
+ *
+ * <p>Note: This class use {@link BloomFilter64} as a base filter. Store the num hash function (one
+ * integer) and bit set bytes only. Use {@link HashFunction} to hash the objects, which hash bytes
+ * type(like varchar, binary, etc.) using xx hash, hash numeric type by specified number hash(see
+ * http://web.archive.org/web/20071223173210/http://www.concentric.net/~Ttwang/tech/inthash.htm).
+ */
 public class BloomFilterFileIndex implements FileIndexer {
 
     public static final String BLOOM_FILTER = "bloom";
diff --git a/paimon-common/src/main/java/org/apache/paimon/utils/BloomFilter64.java b/paimon-common/src/main/java/org/apache/paimon/utils/BloomFilter64.java
index a620a73aace1..75b8661a2eba 100644
--- a/paimon-common/src/main/java/org/apache/paimon/utils/BloomFilter64.java
+++ b/paimon-common/src/main/java/org/apache/paimon/utils/BloomFilter64.java
@@ -21,7 +21,7 @@
 import java.util.BitSet;
 
 /** Bloom filter 64 handle 64 bits hash. */
-public class BloomFilter64 {
+public final class BloomFilter64 {
 
     private final BitSet bitSet;
     private final int numBits;