Update AAChartView.kt

charts/src/main/java/com/github/aachartmodel/aainfographics/aachartcreator/AAChartView.kt

@@ -42,6 +42,8 @@ import android.webkit.*
 import com.github.aachartmodel.aainfographics.aatools.AAJSStringPurer
 import com.google.gson.Gson
 import com.google.gson.internal.LinkedTreeMap
+import java.util.*
+import kotlin.collections.HashMap
 
 
 class AAMoveOverEventMessageModel {
@@ -196,7 +198,7 @@ class AAChartView : WebView {
 
             //convert fist character to be lowercase string
             val firstChar = classNameStr.substring(0, 1)
-            val lowercaseFirstStr = firstChar.toLowerCase()
+            val lowercaseFirstStr = firstChar.toLowerCase(Locale.ROOT)
             classNameStr = classNameStr.substring(1)
             val finalClassName = lowercaseFirstStr + classNameStr
             val finalOptionsMap = HashMap<String, Any>()