Run java class file after button click?

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Java

i have created a simple demo data transfer program.
i want to run main class file, when i click the button.

my class name is invoicegenerator

and
i have a frame class called invoicebuilder. i have insert menu's into invoicebuilder as well.
under invoicebuilder there is an internalframe called invoiceMaker
and there are few buttons in that invoiceMaker internal form.
so now i want to click the button on invoicemaker form
and it should run invoicegenerator class without closing anybackground forms.

What I have tried:

private void cusCancelBtnActionPerformed(java.awt.event.ActionEvent evt)
{
InvoiceGenerator obj=new InvoiceGenerator();
String[] args = {};
obj.main(args);
}
this will run the InvoiceGenerator class, when i click print button. but it will close the form window.