Issue #134 fix show series in legend logic

xchart/src/main/java/org/knowm/xchart/internal/Series.java

@@ -33,7 +33,7 @@ public abstract class Series {
 
   private Color fillColor;
 
-  private boolean showInLegend;
+  private boolean showInLegend = true;
 
   /**
    * Constructor

xchart/src/main/java/org/knowm/xchart/internal/chartpart/Legend_.java

@@ -136,7 +136,7 @@ public abstract class Legend_<ST extends Styler, S extends Series> implements Ch
     Map<String, S> map = chart.getSeriesMap();
     for (Series series : map.values()) {
 
-      if (series.isShowInLegend()) {
+      if (!series.isShowInLegend()) {
         continue;
       }
 

xchart/src/main/java/org/knowm/xchart/internal/chartpart/Legend_AxesChart.java

@@ -69,7 +69,7 @@ public class Legend_AxesChart<ST extends Styler_AxesChart, S extends Series> ext
     Map<String, Series_AxesChart> map = chart.getSeriesMap();
     for (Series_AxesChart series : map.values()) {
 
-      if (series.isShowInLegend()) {
+      if (!series.isShowInLegend()) {
         continue;
       }
 

xchart/src/main/java/org/knowm/xchart/internal/chartpart/Legend_Pie.java

@@ -66,7 +66,7 @@ public class Legend_Pie<ST extends Styler_AxesChart, S extends Series> extends L
     Map<String, Series> map = chart.getSeriesMap();
     for (Series series : map.values()) {
 
-      if (series.isShowInLegend()) {
+      if (!series.isShowInLegend()) {
         continue;
       }