Add bloom filters

java/org/rocksdb/Options.java

@@ -143,6 +143,28 @@ public class Options {
     assert(isInitialized());
     return blockSize(nativeHandle_);
   }
+  
+  /**
+   * Filters are stored in rocksdb and are consulted automatically
+   * by rocksdb to decide whether or not to read some
+   * information from disk. In many cases, a filter can cut down the
+   * number of disk seeks form a handful to a single disk seek per
+   * DB::Get() call.
+   * 
+   * This function a new filter policy that uses a bloom filter 
+   * with approximately the specified number of bits per key.  
+   * A good value for bitsPerKey is 10, which yields a filter 
+   * with ~ 1% false positive rate.
+   * 
+   * @param Bits per key for bloom filter.
+   * @return the instance of the current Options.
+   * @see RocksDB.open()
+   */
+  public Options createBloomFilter(int bitsPerKey) {
+    assert(isInitialized());
+    createBloomFilter0(nativeHandle_, bitsPerKey);
+    return this;
+  }
 
   /*
    * Disable compaction triggered by seek.
@@ -1237,6 +1259,8 @@ public class Options {
 
   private native void useFixedLengthPrefixExtractor(
       long handle, int prefixLength);
+  
+  private native void createBloomFilter0(long handle, int bitsPerKey);
 
   long nativeHandle_;
   long cacheSize_;