Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Logg
er
at org.jfree.chart.axis.Axis.<clinit>(Axis.java:169)
at org.jfree.chart.ChartFactory.createBarChart3D(ChartFactory.java:506)
at BarChartDemo.main(BarChartDemo.java:18)