add Visualize Util and migrate visualize structure to there

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

@@ -197,15 +197,6 @@ object NDArray extends NDArrayBase {
       "_onehot_encode", Seq(indices, out), Map("out" -> out))(0)
   }
 
-  /**
-    * Get the String representation of NDArray
-    * @param nd input NDArray
-    * @return String
-    */
-  def toString(nd : NDArray) : String = {
-    nd.visualize
-  }
-
   /**
    * Create an empty uninitialized new NDArray, with specified shape.
    *
@@ -704,53 +695,7 @@ class NDArray private[mxnet](private[mxnet] val handle: NDArrayHandle,
   }
 
   override def toString() : String = {
-    s"${this.visualize}<NDArray ${this.shape} ${this.context}>"
-  }
-
-  /**
-    * Visualize the internal structure of NDArray
-    * @return String that show the structure
-    */
-  def visualize: String = {
-    buildStringHelper(this, this.shape.length) + "\n"
-  }
-  /**
-    * Helper function to create formatted NDArray output
-    * The NDArray will be represented in a reduced version if too large
-    * @param nd NDArray as the input
-    * @param totalSpace totalSpace of the lowest dimension
-    * @return String format of NDArray
-    */
-  private def buildStringHelper(nd : NDArray, totalSpace : Int) : String = {
-    var result = ""
-    val THRESHOLD = 100000      // longest NDArray to show in full
-    val ARRAYTHRESHOLD = 1000   // longest array to show in full
-    val shape = nd.shape
-    val space = totalSpace - shape.length
-    if (shape.length != 1) {
-      val (length, postfix) =
-        if (shape.product > THRESHOLD) {
-          // reduced NDArray
-          (1, s"\n${" " * (space + 1)}... with length ${shape(0)}\n")
-        } else {
-          (shape(0), "")
-        }
-      for (num <- 0 until length) {
-        val output = buildStringHelper(nd.at(num), totalSpace)
-        result += s"$output\n"
-      }
-      result = s"${" " * space}[\n$result${" " * space}$postfix]"
-    } else {
-      if (shape(0) > ARRAYTHRESHOLD) {
-        // reduced Array
-        val front = nd.slice(0, 10)
-        val back = nd.slice(shape(0) - 10, shape(0) - 1)
-        result = s"${" " * space}[${front.toArray.mkString(",")} ... ${back.toArray.mkString(",")}]"
-      } else {
-        result = s"${" " * space}[${nd.toArray.mkString(",")}]"
-      }
-    }
-    result
+    s"<NDArray ${this.shape} ${this.context}>"
   }
 
   /**

scala-package/core/src/main/scala/org/apache/mxnet/util/Visualize.scala

@@ -0,0 +1,73 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.mxnet.util
+
+import org.apache.mxnet.{NDArray, Shape}
+
+/**
+  * A visualize helper class to see the internal structure
+  * of mxnet data-structure
+  */
+object Visualize {
+
+  /**
+    * Visualize the internal structure of NDArray
+    * @return String that show the structure
+    */
+  def toString(nd : NDArray): String = {
+    buildStringHelper(nd, nd.shape.length) + "\n"
+  }
+  /**
+    * Helper function to create formatted NDArray output
+    * The NDArray will be represented in a reduced version if too large
+    * @param nd NDArray as the input
+    * @param totalSpace totalSpace of the lowest dimension
+    * @return String format of NDArray
+    */
+  private def buildStringHelper(nd : NDArray, totalSpace : Int) : String = {
+    var result = ""
+    val THRESHOLD = 100000      // longest NDArray to show in full
+    val ARRAYTHRESHOLD = 1000   // longest array to show in full
+    val shape = nd.shape
+    val space = totalSpace - shape.length
+    if (shape.length != 1) {
+      val (length, postfix) =
+        if (shape.product > THRESHOLD) {
+          // reduced NDArray
+          (1, s"\n${" " * (space + 1)}... with length ${shape(0)}\n")
+        } else {
+          (shape(0), "")
+        }
+      for (num <- 0 until length) {
+        val output = buildStringHelper(nd.at(num), totalSpace)
+        result += s"$output\n"
+      }
+      result = s"${" " * space}[\n$result${" " * space}$postfix]"
+    } else {
+      if (shape(0) > ARRAYTHRESHOLD) {
+        // reduced Array
+        val front = nd.slice(0, 10)
+        val back = nd.slice(shape(0) - 10, shape(0) - 1)
+        result = s"${" " * space}[${front.toArray.mkString(",")} ... ${back.toArray.mkString(",")}]"
+      } else {
+        result = s"${" " * space}[${nd.toArray.mkString(",")}]"
+      }
+    }
+    result
+  }
+}