解决JXL调用copySheet()和importSheet()方法时报异常的jar包

Java代码java.lang.NullPointerExceptionatjxl.write.biff.WritableSheetCopier.shallowCopyCells(WritableSheetCopier.java:499)[jxl.jar:na]atjxl.write.biff.WritableSheetCopier.copySheet(WritableSheetCopier.java:239)[jxl.jar:na]atjxl.write.biff.WritableSheetImpl.copy(WritableSheetImpl.java:1622)[j