This tutorial will teach you  to make a small Fish shop Inventory  system using Java. The following  system will use to manage the Fish shop. paste the code inside the ok button String item = txtstatus.getSelectedItem().toString(); double fish = Double.parseDouble(txtqty.getText()); if(item.equals("KG")) { double cal = (fish * 140) ; txtbill.setText(String.valueOf(cal)); } else { double cal = (fish/1000 * 140) ; …