diff --git a/pom.xml b/pom.xml
index 6a4b205..7b8cd4a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -13,7 +13,7 @@
     <description>voucher NO. generator</description>
     <url>http://github.com/bingoohuang/voucher-no</url>
     <properties>
-        <java.version>1.6</java.version>
+        <java.version>1.8</java.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <maven.compiler.source>${java.version}</maven.compiler.source>
@@ -67,14 +67,14 @@
         <dependency>
             <groupId>com.google.truth</groupId>
             <artifactId>truth</artifactId>
-            <version>0.33</version>
+            <version>0.40</version>
             <scope>test</scope>
         </dependency>
 
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
-            <version>1.7.25</version>
+            <version>1.8.0-beta2</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -91,7 +91,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
-                <version>2.2.1</version>
+                <version>3.0.1</version>
                 <executions>
                     <execution>
                         <id>attach-sources</id>
@@ -105,7 +105,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>2.9.1</version>
+                <version>3.0.1</version>
                 <executions>
                     <execution>
                         <id>attach-javadocs</id>
@@ -134,7 +134,7 @@
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.7.6.201602180812</version>
+                <version>0.8.1</version>
                 <executions>
                     <execution>
                         <id>prepare-agent</id>
diff --git a/src/main/java/com/github/bingoohuang/voucherno/BloomFilter.java b/src/main/java/com/github/bingoohuang/voucherno/BloomFilter.java
index 0aa25ed..55af43e 100644
--- a/src/main/java/com/github/bingoohuang/voucherno/BloomFilter.java
+++ b/src/main/java/com/github/bingoohuang/voucherno/BloomFilter.java
@@ -65,7 +65,7 @@ public boolean add(String element) {
     public boolean add(byte[] bytes) {
         int[] hashes = createHashes(bytes);
 
-        return bitSet.set(hashes) > 0;
+        return bitSet.add(hashes);
     }
 
     /**
@@ -91,7 +91,7 @@ public boolean contains(String element) {
     public boolean contains(byte[] bytes) {
         int[] hashes = createHashes(bytes);
 
-        return bitSet.get(hashes) == 0;
+        return bitSet.contains(hashes);
     }
 
     private int[] createHashes(byte[] bytes) {
diff --git a/src/main/java/com/github/bingoohuang/voucherno/RedisBitSet.java b/src/main/java/com/github/bingoohuang/voucherno/RedisBitSet.java
index 5d63667..255f1b8 100644
--- a/src/main/java/com/github/bingoohuang/voucherno/RedisBitSet.java
+++ b/src/main/java/com/github/bingoohuang/voucherno/RedisBitSet.java
@@ -5,44 +5,26 @@
 import redis.clients.jedis.BinaryJedis;
 import redis.clients.jedis.Protocol;
 
-import java.util.List;
+import java.util.Arrays;
 
 public class RedisBitSet {
-    private BinaryJedis jedis;
-    private byte[] name;
+    private final BinaryJedis jedis;
+    private final byte[] name;
 
     public RedisBitSet(BinaryJedis jedis, String name) {
         this.jedis = jedis;
         this.name = name.getBytes(MessageDigestUtils.UTF8);
     }
 
-    public int set(int[] hashes) {
+    public boolean add(int[] hashes) {
         val multi = jedis.multi();
-        for (int hash : hashes) {
-            multi.setbit(name, hash, Protocol.BYTES_TRUE);
-        }
-        val result = multi.exec();
-
-        int oks = 0;
-        for (val obj : result) {
-            if (obj == Boolean.FALSE) ++oks;
-        }
-
-        return oks;
+        Arrays.stream(hashes).forEach(x -> multi.setbit(name, x, Protocol.BYTES_TRUE));
+        return multi.exec().stream().filter(x -> x == Boolean.FALSE).count() > 0;
     }
 
-    public int get(int[] hashes) {
+    public boolean contains(int[] hashes) {
         val multi = jedis.multi();
-        for (int hash : hashes) {
-            multi.getbit(name, hash);
-        }
-        List<Object> result = multi.exec();
-
-        int falses = 0;
-        for (val obj : result) {
-            if (obj == Boolean.FALSE) ++falses;
-        }
-
-        return falses;
+        Arrays.stream(hashes).forEach(x -> multi.getbit(name, x));
+        return multi.exec().stream().filter(x -> x == Boolean.FALSE).count() == 0;
     }
 }
\ No newline at end of file