diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.java
deleted file mode 100644
index 06bc6d9f15..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.java
+++ /dev/null
@@ -1,113 +0,0 @@
-
-package com.github.mikephil.charting.data;
-
-import com.github.mikephil.charting.interfaces.datasets.IBarDataSet;
-
-import java.util.List;
-
-/**
- * Data object that represents all data for the BarChart.
- *
- * @author Philipp Jahoda
- */
-public class BarData extends BarLineScatterCandleBubbleData<IBarDataSet> {
-
-    /**
-     * the width of the bars on the x-axis, in values (not pixels)
-     */
-    private float mBarWidth = 0.85f;
-
-    public BarData() {
-        super();
-    }
-
-    public BarData(IBarDataSet... dataSets) {
-        super(dataSets);
-    }
-
-    public BarData(List<IBarDataSet> dataSets) {
-        super(dataSets);
-    }
-
-    /**
-     * Sets the width each bar should have on the x-axis (in values, not pixels).
-     * Default 0.85f
-     */
-    public void setBarWidth(float mBarWidth) {
-        this.mBarWidth = mBarWidth;
-    }
-
-    public float getBarWidth() {
-        return mBarWidth;
-    }
-
-    /**
-     * Groups all BarDataSet objects this data object holds together by modifying the x-value of their entries.
-     * Previously set x-values of entries will be overwritten. Leaves space between bars and groups as specified
-     * by the parameters.
-     * Do not forget to call notifyDataSetChanged() on your BarChart object after calling this method.
-     *
-     * @param fromX      the starting point on the x-axis where the grouping should begin
-     * @param groupSpace the space between groups of bars in values (not pixels) e.g. 0.8f for bar width 1f
-     * @param barSpace   the space between individual bars in values (not pixels) e.g. 0.1f for bar width 1f
-     */
-    public void groupBars(float fromX, float groupSpace, float barSpace) {
-
-        int setCount = mDataSets.size();
-        if (setCount <= 1) {
-            throw new RuntimeException("BarData needs to hold at least 2 BarDataSets to allow grouping.");
-        }
-
-        IBarDataSet max = getMaxEntryCountSet();
-        int maxEntryCount = max.getEntryCount();
-
-        float groupSpaceWidthHalf = groupSpace / 2f;
-        float barSpaceHalf = barSpace / 2f;
-        float barWidthHalf = mBarWidth / 2f;
-
-        float interval = getGroupWidth(groupSpace, barSpace);
-
-        for (int i = 0; i < maxEntryCount; i++) {
-
-            float start = fromX;
-            fromX += groupSpaceWidthHalf;
-
-            for (IBarDataSet set : mDataSets) {
-
-                fromX += barSpaceHalf;
-                fromX += barWidthHalf;
-
-                if (i < set.getEntryCount()) {
-
-                    BarEntry entry = set.getEntryForIndex(i);
-
-                    if (entry != null) {
-                        entry.setX(fromX);
-                    }
-                }
-
-                fromX += barWidthHalf;
-                fromX += barSpaceHalf;
-            }
-
-            fromX += groupSpaceWidthHalf;
-            float end = fromX;
-            float innerInterval = end - start;
-            float diff = interval - innerInterval;
-
-            // correct rounding errors
-            if (diff > 0 || diff < 0) {
-                fromX += diff;
-            }
-        }
-
-        notifyDataChanged();
-    }
-
-    /**
-     * In case of grouped bars, this method returns the space an individual group of bar needs on the x-axis.
-     */
-    public float getGroupWidth(float groupSpace, float barSpace) {
-        return mDataSets.size() * (mBarWidth + barSpace) + groupSpace;
-    }
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.kt
new file mode 100644
index 0000000000..15967fe109
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BarData.kt
@@ -0,0 +1,90 @@
+package com.github.mikephil.charting.data
+
+import com.github.mikephil.charting.interfaces.datasets.IBarDataSet
+
+/**
+ * Data object that represents all data for the BarChart.
+ */
+class BarData : BarLineScatterCandleBubbleData<IBarDataSet> {
+    /**
+     * Sets the width each bar should have on the x-axis (in values, not pixels).
+     * Default 0.85f
+     */
+    /**
+     * the width of the bars on the x-axis, in values (not pixels)
+     */
+    var barWidth: Float = 0.85f
+
+    constructor() : super()
+
+    constructor(vararg dataSets: IBarDataSet) : super(*dataSets)
+
+    constructor(dataSets: MutableList<IBarDataSet>) : super(dataSets)
+
+    /**
+     * Groups all BarDataSet objects this data object holds together by modifying the x-value of their entries.
+     * Previously set x-values of entries will be overwritten. Leaves space between bars and groups as specified
+     * by the parameters.
+     * Do not forget to call notifyDataSetChanged() on your BarChart object after calling this method.
+     *
+     * @param fromX      the starting point on the x-axis where the grouping should begin
+     * @param groupSpace the space between groups of bars in values (not pixels) e.g. 0.8f for bar width 1f
+     * @param barSpace   the space between individual bars in values (not pixels) e.g. 0.1f for bar width 1f
+     */
+    fun groupBars(fromX: Float, groupSpace: Float, barSpace: Float) {
+        var fromX = fromX
+        val setCount = mDataSets.size
+        if (setCount <= 1) {
+            throw RuntimeException("BarData needs to hold at least 2 BarDataSets to allow grouping.")
+        }
+
+        val max = getMaxEntryCountSet()
+        val maxEntryCount = max.entryCount
+
+        val groupSpaceWidthHalf = groupSpace / 2f
+        val barSpaceHalf = barSpace / 2f
+        val barWidthHalf = this.barWidth / 2f
+
+        val interval = getGroupWidth(groupSpace, barSpace)
+
+        for (i in 0..<maxEntryCount) {
+            val start = fromX
+            fromX += groupSpaceWidthHalf
+
+            for (set in mDataSets) {
+                fromX += barSpaceHalf
+                fromX += barWidthHalf
+
+                if (i < set.entryCount) {
+                    val entry = set.getEntryForIndex(i)
+
+                    if (entry != null) {
+                        entry.x = fromX
+                    }
+                }
+
+                fromX += barWidthHalf
+                fromX += barSpaceHalf
+            }
+
+            fromX += groupSpaceWidthHalf
+            val end = fromX
+            val innerInterval = end - start
+            val diff = interval - innerInterval
+
+            // correct rounding errors
+            if (diff !in 0.0..0.0) {
+                fromX += diff
+            }
+        }
+
+        notifyDataChanged()
+    }
+
+    /**
+     * In case of grouped bars, this method returns the space an individual group of bar needs on the x-axis.
+     */
+    fun getGroupWidth(groupSpace: Float, barSpace: Float): Float {
+        return mDataSets.size * (this.barWidth + barSpace) + groupSpace
+    }
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.java
deleted file mode 100644
index 680170c55c..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.java
+++ /dev/null
@@ -1,32 +0,0 @@
-
-package com.github.mikephil.charting.data;
-
-import com.github.mikephil.charting.interfaces.datasets.IBubbleDataSet;
-
-import java.util.List;
-
-public class BubbleData extends BarLineScatterCandleBubbleData<IBubbleDataSet> {
-
-    public BubbleData() {
-        super();
-    }
-
-    public BubbleData(IBubbleDataSet... dataSets) {
-        super(dataSets);
-    }
-
-    public BubbleData(List<IBubbleDataSet> dataSets) {
-        super(dataSets);
-    }
-
-
-    /**
-     * Sets the width of the circle that surrounds the bubble when highlighted
-     * for all DataSet objects this data object contains, in dp.
-     */
-    public void setHighlightCircleWidth(float width) {
-        for (IBubbleDataSet set : mDataSets) {
-            set.setHighlightCircleWidth(width);
-        }
-    }
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.kt
new file mode 100644
index 0000000000..4b403c307c
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/BubbleData.kt
@@ -0,0 +1,22 @@
+package com.github.mikephil.charting.data
+
+import com.github.mikephil.charting.interfaces.datasets.IBubbleDataSet
+
+class BubbleData : BarLineScatterCandleBubbleData<IBubbleDataSet> {
+    constructor() : super()
+
+    constructor(vararg dataSets: IBubbleDataSet) : super(*dataSets)
+
+    constructor(dataSets: MutableList<IBubbleDataSet>) : super(dataSets)
+
+
+    /**
+     * Sets the width of the circle that surrounds the bubble when highlighted
+     * for all DataSet objects this data object contains, in dp.
+     */
+    fun setHighlightCircleWidth(width: Float) {
+        for (set in mDataSets) {
+            set.highlightCircleWidth = width
+        }
+    }
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.java
deleted file mode 100644
index 73728c91a7..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.java
+++ /dev/null
@@ -1,20 +0,0 @@
-package com.github.mikephil.charting.data;
-
-import com.github.mikephil.charting.interfaces.datasets.ICandleDataSet;
-
-import java.util.List;
-
-public class CandleData extends BarLineScatterCandleBubbleData<ICandleDataSet> {
-
-	public CandleData() {
-		super();
-	}
-
-	public CandleData(List<ICandleDataSet> dataSets) {
-		super(dataSets);
-	}
-
-	public CandleData(ICandleDataSet... dataSets) {
-		super(dataSets);
-	}
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.kt
new file mode 100644
index 0000000000..02375528cc
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/CandleData.kt
@@ -0,0 +1,11 @@
+package com.github.mikephil.charting.data
+
+import com.github.mikephil.charting.interfaces.datasets.ICandleDataSet
+
+class CandleData : BarLineScatterCandleBubbleData<ICandleDataSet> {
+    constructor() : super()
+
+    constructor(dataSets: MutableList<ICandleDataSet>) : super(dataSets)
+
+    constructor(vararg dataSets: ICandleDataSet) : super(*dataSets)
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.java
deleted file mode 100644
index 29ae51ae9e..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.java
+++ /dev/null
@@ -1,90 +0,0 @@
-
-package com.github.mikephil.charting.data;
-
-import android.util.Log;
-
-import com.github.mikephil.charting.highlight.Highlight;
-import com.github.mikephil.charting.interfaces.datasets.IPieDataSet;
-
-import java.util.List;
-
-/**
- * A PieData object can only represent one DataSet. Unlike all other charts, the
- * legend labels of the PieChart are created from the x-values array, and not
- * from the DataSet labels. Each PieData object can only represent one
- * PieDataSet (multiple PieDataSets inside a single PieChart are not possible).
- *
- * @author Philipp Jahoda
- */
-public class PieData extends ChartData<IPieDataSet> {
-
-    public PieData() {
-        super();
-    }
-
-    public PieData(IPieDataSet dataSet) {
-        super(dataSet);
-    }
-
-    /**
-     * Sets the PieDataSet this data object should represent.
-     */
-    public void setDataSet(IPieDataSet dataSet) {
-        mDataSets.clear();
-        mDataSets.add(dataSet);
-        notifyDataChanged();
-    }
-
-    /**
-     * Returns the DataSet this PieData object represents. A PieData object can
-     * only contain one DataSet.
-     */
-    public IPieDataSet getDataSet() {
-        return mDataSets.get(0);
-    }
-
-    @Override
-    public List<IPieDataSet> getDataSets() {
-        List<IPieDataSet> dataSets = super.getDataSets();
-
-        if (dataSets.isEmpty()) {
-            Log.e("AndroidChart",
-                    "Found multiple data sets while pie chart only allows one");
-        }
-
-        return dataSets;
-    }
-
-    /**
-     * The PieData object can only have one DataSet. Use getDataSet() method instead.
-     */
-    @Override
-    public IPieDataSet getDataSetByIndex(int index) {
-        return index == 0 ? getDataSet() : null;
-    }
-
-    @Override
-    public IPieDataSet getDataSetByLabel(String label, boolean ignorecase) {
-        return ignorecase ? label.equalsIgnoreCase(mDataSets.get(0).getLabel()) ? mDataSets.get(0)
-                : null : label.equals(mDataSets.get(0).getLabel()) ? mDataSets.get(0) : null;
-    }
-
-    @Override
-    public Entry getEntryForHighlight(Highlight highlight) {
-        return getDataSet().getEntryForIndex((int) highlight.getX());
-    }
-
-    /**
-     * Returns the sum of all values in this PieData object.
-     */
-    public float getYValueSum() {
-
-        float sum = 0;
-
-        for (int i = 0; i < getDataSet().getEntryCount(); i++)
-            sum += getDataSet().getEntryForIndex(i).getY();
-
-
-        return sum;
-    }
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.kt
new file mode 100644
index 0000000000..15e2baadc1
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/PieData.kt
@@ -0,0 +1,76 @@
+package com.github.mikephil.charting.data
+
+import android.util.Log
+import com.github.mikephil.charting.highlight.Highlight
+import com.github.mikephil.charting.interfaces.datasets.IPieDataSet
+
+/**
+ * A PieData object can only represent one DataSet. Unlike all other charts, the
+ * legend labels of the PieChart are created from the x-values array, and not
+ * from the DataSet labels. Each PieData object can only represent one
+ * PieDataSet (multiple PieDataSets inside a single PieChart are not possible).
+ */
+class PieData : ChartData<IPieDataSet?> {
+    constructor() : super()
+
+    constructor(dataSet: IPieDataSet?) : super(dataSet)
+
+    var dataSet: IPieDataSet?
+        /**
+         * Returns the DataSet this PieData object represents. A PieData object can
+         * only contain one DataSet.
+         */
+        get() = mDataSets[0]
+        /**
+         * Sets the PieDataSet this data object should represent.
+         */
+        set(dataSet) {
+            mDataSets.clear()
+            mDataSets.add(dataSet)
+            notifyDataChanged()
+        }
+
+    override fun getDataSets(): MutableList<IPieDataSet?> {
+        val dataSets = super.getDataSets()
+
+        if (dataSets.isEmpty()) {
+            Log.e(
+                "AndroidChart",
+                "Found multiple data sets while pie chart only allows one"
+            )
+        }
+
+        return dataSets
+    }
+
+    /**
+     * The PieData object can only have one DataSet. Use getDataSet() method instead.
+     */
+    override fun getDataSetByIndex(index: Int): IPieDataSet? {
+        return if (index == 0) this.dataSet else null
+    }
+
+    override fun getDataSetByLabel(label: String, ignorecase: Boolean): IPieDataSet? {
+        return if (ignorecase) if (label.equals(mDataSets[0]!!.label, ignoreCase = true))
+            mDataSets[0]
+        else
+            null else if (label == mDataSets[0]!!.label) mDataSets[0] else null
+    }
+
+    override fun getEntryForHighlight(highlight: Highlight): Entry? {
+        return this.dataSet!!.getEntryForIndex(highlight.x.toInt())
+    }
+
+    val yValueSum: Float
+        /**
+         * Returns the sum of all values in this PieData object.
+         */
+        get() {
+            var sum = 0f
+
+            for (i in 0..<this.dataSet!!.entryCount) sum += this.dataSet!!.getEntryForIndex(i)!!.y
+
+
+            return sum
+        }
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.java
deleted file mode 100644
index 0c1dbe5505..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.java
+++ /dev/null
@@ -1,58 +0,0 @@
-
-package com.github.mikephil.charting.data;
-
-import com.github.mikephil.charting.highlight.Highlight;
-import com.github.mikephil.charting.interfaces.datasets.IRadarDataSet;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-
-/**
- * Data container for the RadarChart.
- *
- * @author Philipp Jahoda
- */
-public class RadarData extends ChartData<IRadarDataSet> {
-
-    private List<String> mLabels;
-
-    public RadarData() {
-        super();
-    }
-
-    public RadarData(List<IRadarDataSet> dataSets) {
-        super(dataSets);
-    }
-
-    public RadarData(IRadarDataSet... dataSets) {
-        super(dataSets);
-    }
-
-    /**
-     * Sets the labels that should be drawn around the RadarChart at the end of each web line.
-     *
-     * @param labels
-     */
-    public void setLabels(List<String> labels) {
-        this.mLabels = labels;
-    }
-
-    /**
-     * Sets the labels that should be drawn around the RadarChart at the end of each web line.
-     *
-     * @param labels
-     */
-    public void setLabels(String... labels) {
-        this.mLabels = Arrays.asList(labels);
-    }
-
-    public List<String> getLabels() {
-        return mLabels;
-    }
-
-    @Override
-    public Entry getEntryForHighlight(Highlight highlight) {
-        return getDataSetByIndex(highlight.getDataSetIndex()).getEntryForIndex((int) highlight.getX());
-    }
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.kt
new file mode 100644
index 0000000000..aeb82dd1e8
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/RadarData.kt
@@ -0,0 +1,36 @@
+package com.github.mikephil.charting.data
+
+import com.github.mikephil.charting.highlight.Highlight
+import com.github.mikephil.charting.interfaces.datasets.IRadarDataSet
+import java.util.Arrays
+
+/**
+ * Data container for the RadarChart.
+ */
+class RadarData : ChartData<IRadarDataSet> {
+    /**
+     * Sets the labels that should be drawn around the RadarChart at the end of each web line.
+     *
+     * @param labels
+     */
+    var labels: MutableList<String?>? = null
+
+    constructor() : super()
+
+    constructor(dataSets: MutableList<IRadarDataSet?>) : super(dataSets)
+
+    constructor(vararg dataSets: IRadarDataSet) : super(*dataSets)
+
+    /**
+     * Sets the labels that should be drawn around the RadarChart at the end of each web line.
+     *
+     * @param labels
+     */
+    fun setLabels(vararg labels: String?) {
+        this.labels = Arrays.asList<String?>(*labels)
+    }
+
+    override fun getEntryForHighlight(highlight: Highlight): Entry? {
+        return getDataSetByIndex(highlight.dataSetIndex)!!.getEntryForIndex(highlight.x.toInt())
+    }
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.java b/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.java
deleted file mode 100644
index 360efc2904..0000000000
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.java
+++ /dev/null
@@ -1,38 +0,0 @@
-
-package com.github.mikephil.charting.data;
-
-import com.github.mikephil.charting.interfaces.datasets.IScatterDataSet;
-
-import java.util.List;
-
-public class ScatterData extends BarLineScatterCandleBubbleData<IScatterDataSet> {
-
-    public ScatterData() {
-        super();
-    }
-
-    public ScatterData(List<IScatterDataSet> dataSets) {
-        super(dataSets);
-    }
-
-    public ScatterData(IScatterDataSet... dataSets) {
-        super(dataSets);
-    }
-
-    /**
-     * Returns the maximum shape-size across all DataSets.
-     */
-    public float getGreatestShapeSize() {
-
-        float max = 0f;
-
-        for (IScatterDataSet set : mDataSets) {
-            float size = set.getScatterShapeSize();
-
-            if (size > max)
-                max = size;
-        }
-
-        return max;
-    }
-}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.kt
new file mode 100644
index 0000000000..69c13d39f9
--- /dev/null
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/data/ScatterData.kt
@@ -0,0 +1,27 @@
+package com.github.mikephil.charting.data
+
+import com.github.mikephil.charting.interfaces.datasets.IScatterDataSet
+
+class ScatterData : BarLineScatterCandleBubbleData<IScatterDataSet> {
+    constructor() : super()
+
+    constructor(dataSets: MutableList<IScatterDataSet>) : super(dataSets)
+
+    constructor(vararg dataSets: IScatterDataSet) : super(*dataSets)
+
+    val greatestShapeSize: Float
+        /**
+         * Returns the maximum shape-size across all DataSets.
+         */
+        get() {
+            var max = 0f
+
+            for (set in mDataSets) {
+                val size = set.scatterShapeSize
+
+                if (size > max) max = size
+            }
+
+            return max
+        }
+}
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/highlight/PieHighlighter.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/highlight/PieHighlighter.kt
index 728b7ae17a..d662bc50b3 100644
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/highlight/PieHighlighter.kt
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/highlight/PieHighlighter.kt
@@ -7,7 +7,7 @@ class PieHighlighter(chart: PieChart) : PieRadarHighlighter<PieChart>(chart) {
     override fun getClosestHighlight(index: Int, x: Float, y: Float): Highlight? {
         val pieDataSet = chart!!.data!!.dataSet
 
-        val entry: Entry? = pieDataSet.getEntryForIndex(index)
+        val entry: Entry? = pieDataSet?.getEntryForIndex(index)
 
         entry?.let {
             return Highlight(index.toFloat(), entry.y, x, y, 0, pieDataSet.axisDependency)
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.kt b/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.kt
index 60eace4df3..9db6103ea2 100644
--- a/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.kt
+++ b/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.kt
@@ -104,7 +104,7 @@ open class PieChartRenderer(
         val pieData = chart.data
 
         for (set in pieData!!.dataSets) {
-            if (set.isVisible && set.entryCount > 0) drawDataSet(set)
+            if (set!!.isVisible && set.entryCount > 0) drawDataSet(set)
         }
     }
 
@@ -389,7 +389,7 @@ open class PieChartRenderer(
 
             for (i in dataSets.indices) {
                 val dataSet = dataSets[i]
-                if (dataSet.entryCount == 0) {
+                if (dataSet!!.entryCount == 0) {
                     continue
                 }
                 val drawValues = dataSet.isDrawValues
@@ -900,11 +900,13 @@ open class PieChartRenderer(
      * This gives all pie-slices a rounded edge.
      */
     protected fun drawRoundedSlices() {
-        if (!chart.isDrawRoundedSlicesEnabled) return
+        if (!chart.isDrawRoundedSlicesEnabled)
+            return
 
         val dataSet = chart.data!!.dataSet
 
-        if (!dataSet.isVisible) return
+        if (!dataSet!!.isVisible)
+            return
 
         val phaseX = animator.phaseX
         val phaseY = animator.phaseY
diff --git a/app/src/main/kotlin/info/appdev/chartexample/AnotherBarActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/AnotherBarActivity.kt
index 16ca4d0fc1..4e67247fe8 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/AnotherBarActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/AnotherBarActivity.kt
@@ -98,7 +98,7 @@ class AnotherBarActivity : DemoBase(), OnSeekBarChangeListener {
             set1.setColors(*ColorTemplate.VORDIPLOM_COLORS)
             set1.isDrawValues = false
 
-            val dataSets = ArrayList<IBarDataSet?>()
+            val dataSets = ArrayList<IBarDataSet>()
             dataSets.add(set1)
 
             val data = BarData(dataSets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/BarChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/BarChartActivity.kt
index 176f5eeef0..443b43d77a 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/BarChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/BarChartActivity.kt
@@ -176,7 +176,7 @@ class BarChartActivity : DemoBase(), OnSeekBarChangeListener, OnChartValueSelect
 
             set1.fills = gradientFills
 
-            val dataSets = ArrayList<IBarDataSet?>()
+            val dataSets = ArrayList<IBarDataSet>()
             dataSets.add(set1)
 
             val data = BarData(dataSets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/BubbleChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/BubbleChartActivity.kt
index 29bee05eb0..16388d3be6 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/BubbleChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/BubbleChartActivity.kt
@@ -136,7 +136,7 @@ class BubbleChartActivity : DemoBase(), OnSeekBarChangeListener, OnChartValueSel
         set3.setColor(ColorTemplate.COLORFUL_COLORS[2], 130)
         set3.isDrawValues = true
 
-        val dataSets = ArrayList<IBubbleDataSet?>()
+        val dataSets = ArrayList<IBubbleDataSet>()
         dataSets.add(set1) // add the data sets
         dataSets.add(set2)
         dataSets.add(set3)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarChartActivity.kt
index d4e487d1a4..9865a3ffc7 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarChartActivity.kt
@@ -127,7 +127,7 @@ class HorizontalBarChartActivity : DemoBase(), OnSeekBarChangeListener, OnChartV
 
             set1.isDrawIcons = false
 
-            val dataSets = ArrayList<IBarDataSet?>()
+            val dataSets = ArrayList<IBarDataSet>()
             dataSets.add(set1)
 
             val data = BarData(dataSets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarNegativeChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarNegativeChartActivity.kt
index 4deccc1bfb..c9300b99bb 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarNegativeChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/HorizontalBarNegativeChartActivity.kt
@@ -134,7 +134,7 @@ class HorizontalBarNegativeChartActivity : DemoBase(), OnSeekBarChangeListener,
 
             set1.isDrawIcons = false
 
-            val dataSets = ArrayList<IBarDataSet?>()
+            val dataSets = ArrayList<IBarDataSet>()
             dataSets.add(set1)
 
             val data = BarData(dataSets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/ListViewBarChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/ListViewBarChartActivity.kt
index b448b17c42..13d5daec97 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/ListViewBarChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/ListViewBarChartActivity.kt
@@ -123,7 +123,7 @@ class ListViewBarChartActivity : DemoBase() {
         d.setColors(*ColorTemplate.VORDIPLOM_COLORS)
         d.barShadowColor = Color.rgb(203, 203, 203)
 
-        val sets = ArrayList<IBarDataSet?>()
+        val sets = ArrayList<IBarDataSet>()
         sets.add(d)
 
         val cd = BarData(sets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/ScatterChartActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/ScatterChartActivity.kt
index 3cfa0b3e88..9641236e10 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/ScatterChartActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/ScatterChartActivity.kt
@@ -123,7 +123,7 @@ class ScatterChartActivity : DemoBase(), OnSeekBarChangeListener, OnChartValueSe
         set2.scatterShapeSize = 8f
         set3.scatterShapeSize = 8f
 
-        val dataSets = ArrayList<IScatterDataSet?>()
+        val dataSets = ArrayList<IScatterDataSet>()
         dataSets.add(set1) // add the data sets
         dataSets.add(set2)
         dataSets.add(set3)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/StackedBarActivity.kt b/app/src/main/kotlin/info/appdev/chartexample/StackedBarActivity.kt
index 7607862b62..fa05b19686 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/StackedBarActivity.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/StackedBarActivity.kt
@@ -132,7 +132,7 @@ class StackedBarActivity : DemoBase(), OnSeekBarChangeListener, OnChartValueSele
             set1.setColors(*this.colors)
             set1.stackLabels = arrayOf("Births", "Divorces", "Marriages")
 
-            val dataSets = ArrayList<IBarDataSet?>()
+            val dataSets = ArrayList<IBarDataSet>()
             dataSets.add(set1)
 
             val data = BarData(dataSets)
diff --git a/app/src/main/kotlin/info/appdev/chartexample/fragments/SimpleFragment.kt b/app/src/main/kotlin/info/appdev/chartexample/fragments/SimpleFragment.kt
index 8c8b863129..c91ac63773 100644
--- a/app/src/main/kotlin/info/appdev/chartexample/fragments/SimpleFragment.kt
+++ b/app/src/main/kotlin/info/appdev/chartexample/fragments/SimpleFragment.kt
@@ -38,7 +38,7 @@ abstract class SimpleFragment : Fragment() {
     protected fun generateBarData(dataSets: Int, range: Float): BarData {
         val count = 12
         val values = getValues(count)
-        val sets = ArrayList<IBarDataSet?>()
+        val sets = ArrayList<IBarDataSet>()
 
         for (i in 0..<dataSets) {
             val entries = ArrayList<BarEntry>()
@@ -61,7 +61,7 @@ abstract class SimpleFragment : Fragment() {
     protected fun generateScatterData(dataSets: Int, range: Float): ScatterData {
         val count = 100
         val values = getValues(count)
-        val sets = ArrayList<IScatterDataSet?>()
+        val sets = ArrayList<IScatterDataSet>()
 
         val shapes = ScatterShape.getAllDefaultShapes()