framework of xgboost-spark

iterator

return java iterator and recover test

jvm-packages/xgboost4j/src/main/scala/ml/dmlc/xgboost4j/scala/DMatrix.scala

@@ -16,7 +16,9 @@
 
 package ml.dmlc.xgboost4j.scala
 
-import ml.dmlc.xgboost4j.{DMatrix => JDMatrix, XGBoostError}
+import _root_.scala.collection.JavaConverters._
+
+import ml.dmlc.xgboost4j.{DMatrix => JDMatrix, DataBatch, XGBoostError}
 
 class DMatrix private[scala](private[scala] val jDMatrix: JDMatrix) {
 
@@ -43,6 +45,10 @@ class DMatrix private[scala](private[scala] val jDMatrix: JDMatrix) {
     this(new JDMatrix(headers, indices, data, st))
   }
 
+  private[xgboost4j] def this(dataBatch: DataBatch) {
+    this(new JDMatrix(List(dataBatch).asJava.iterator, null))
+  }
+
   /**
    * create DMatrix from dense matrix
    *