fix bug and add tests

scala-package/core/src/main/scala/org/apache/mxnet/NDArray.scala

@@ -449,7 +449,7 @@ object NDArray extends NDArrayBase {
       case arrAny : Array[Any] => {
         val fragment = (end - start + 1) / arrAny.length
         for (i <- arrAny.indices)
-          arrayCombiner(arrAny(i), arr, start + i * fragment, end + (i + 1) * fragment)
+          arrayCombiner(arrAny(i), arr, start + i * fragment, start + (i + 1) * fragment)
       }
       case _ => throw new IllegalArgumentException(s"Wrong type passed: ${sourceArr.getClass}")
     }

scala-package/core/src/test/scala/org/apache/mxnet/NDArraySuite.scala

@@ -21,7 +21,9 @@ import java.io.File
 import java.util.concurrent.atomic.AtomicInteger
 
 import org.apache.mxnet.NDArrayConversions._
-import org.scalatest.{Matchers, BeforeAndAfterAll, FunSuite}
+import org.scalatest.{BeforeAndAfterAll, FunSuite, Matchers}
+
+import scala.collection.mutable.ArrayBuffer
 
 class NDArraySuite extends FunSuite with BeforeAndAfterAll with Matchers {
   private val sequence: AtomicInteger = new AtomicInteger(0)
@@ -65,6 +67,31 @@ class NDArraySuite extends FunSuite with BeforeAndAfterAll with Matchers {
     assert(ndarray.toArray === Array(1f, 2f, 3f, 4f))
   }
 
+  test("create NDArray based on Java Matrix") {
+    val arrBuf = ArrayBuffer[Array[Float]]()
+    for (i <- 0 until 100) arrBuf += Array(1.0f, 1.0f, 1.0f, 1.0f)
+    val arr = Array(
+      Array(
+        arrBuf.toArray
+      ),
+      Array(
+        arrBuf.toArray
+        )
+    )
+    var nd = NDArray.toNDArray(arr)
+    require(nd.shape == Shape(2, 1, 100, 4))
+    val arr2 = Array(1.0f, 1.0f, 1.0f, 1.0f)
+    nd = NDArray.toNDArray(arr2)
+    require(nd.shape == Shape(4))
+  }
+
+  test("test Visualize") {
+    var nd = NDArray.ones(Shape(1, 2, 100, 1))
+    nd.visualize
+    nd = NDArray.ones(Shape(1, 4))
+    nd.visualize
+  }
+
   test("plus") {
     val ndzeros = NDArray.zeros(2, 1)
     val ndones = ndzeros + 1f