How to Define and use Macro in java

import java.io.StringWriter;
import java.io.Writer;

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.tools.generic.RenderTool;

public class VMDemo {

public static void main(String[] args) throws Exception {
Velocity.init();
Template t = Velocity.getTemplate("./src/VMDemo.vm");

VelocityContext ctx = new VelocityContext();

Writer writer = new StringWriter();
t.merge(ctx, writer);

System.out.println(writer);
}
}
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#macro (writeTable $productList)
#set ($rowCount = 1)
#foreach($product in $productList)
#if ($rowCount % 2 == 0)
#set ($bgcolor = "#FFFFFF")
#else
#set ($bgcolor = "#CCCCCC")
#end

$product
$product

#set ($rowCount = $rowCount + 1)
#end
#end

#set ($products = ["one", "two", "three"])






#writeTable($products)