make DecimalFormat private

app/src/main/java/de/beowulf/wetter/adapter/GraphAdapter.kt

@@ -30,7 +30,7 @@ class TempGraphAdapter(context: Context, attributeSet: AttributeSet) : View(cont
     private val dm = resources.displayMetrics
     private val radius = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 5f, dm)
     private var rainUnit = ""
-    val df = DecimalFormat("#.#")
+    private val df = DecimalFormat("#.#")
 
     private val dataPointPaint = Paint().apply {
         context.theme.resolveAttribute(R.attr.colorAccent, typedValue, true)