The border of the icons used in the Legend use the java.awt.Paint Interface to control their appearance.
A value of NULL will draw the icons with no borders. There are several implementations of the java.awt.Paint
Interface in the java.awt Package to choose from.
LegendProperties legendProperties= new LegendProperties();
legendProperties.setIconBorderPaint( Color.red );
We used a Clustered Bar Chart in this example as Line Chart Legend Icons do not have border paints assigned to them.
Point Charts use the Border Paint from the plot area.