diff --git a/jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala b/jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala
index 4bbef3cde..68b887b23 100644
--- a/jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala
+++ b/jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala
@@ -64,7 +64,6 @@ object XGBoost extends Serializable {
       tracker.getWorkerEnvs.asScala, numWorkers, round, obj, eval)
     // force the job
     boosters.foreachPartition(_ => ())
-    println("=====finished training=====")
     val booster = boosters.first()
     val returnVal = tracker.waitFor()
     logger.info(s"Rabit returns with exit code $returnVal")
diff --git a/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostSuite.scala b/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostSuite.scala
index 23c9924d1..ca1fe9ada 100644
--- a/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostSuite.scala
+++ b/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostSuite.scala
@@ -130,6 +130,7 @@ class XGBoostSuite extends FunSuite with BeforeAndAfterAll {
       trainingRDD,
       List("eta" -> "1", "max_depth" -> "2", "silent" -> "0",
         "objective" -> "binary:logistic").toMap,
+      new scala.collection.mutable.HashMap[String, String],
       numWorker, 2, null, null)
     val boosterCount = boosterRDD.count()
     assert(boosterCount === numWorker)
diff --git a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java
index 15e242b6d..5778149f2 100644
--- a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java
+++ b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java
@@ -350,7 +350,10 @@ public class Booster implements  Serializable {
   }
 
   /**
-   * get the dump of the model as a string array
+   * Save the model as byte array representation.
+   * Write these bytes to a file will give compatible format with other xgboost bindings.
+   *
+   * If java natively support HDFS file API, use toByteArray and write the ByteArray
    *
    * @param withStats Controls whether the split statistics are output.
    * @return dumped model information
@@ -367,9 +370,8 @@ public class Booster implements  Serializable {
   }
 
   /**
-   * get the dump of the model as a byte array
    *
-   * @return dumped model information
+   * @return the saved byte array.
    * @throws XGBoostError native error
    */
   public byte[] toByteArray() throws XGBoostError {
diff --git a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/DataBatch.java b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/DataBatch.java
index 82ae97ed6..d2ff3b612 100644
--- a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/DataBatch.java
+++ b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/DataBatch.java
@@ -57,7 +57,7 @@ class DataBatch {
     return b;
   }
 
-  static class BatchIterator implements Iterator<DataBatch>, Serializable {
+  static class BatchIterator implements Iterator<DataBatch> {
     private Iterator<LabeledPoint> base;
     private int batchSize;
 
diff --git a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Rabit.java b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Rabit.java
index e336cf807..3429dc3dd 100644
--- a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Rabit.java
+++ b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Rabit.java
@@ -10,7 +10,7 @@ import org.apache.commons.logging.LogFactory;
 /**
  * Rabit global class for synchronization.
  */
-public class Rabit implements Serializable {
+public class Rabit {
   private static final Log logger = LogFactory.getLog(DMatrix.class);
   //load native library
   static {