Plugin Help me understand it for my serever

package brian;

import org.bukkit.Material;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.PlayerInventory;

public class cmdsmelt implements CommandExecutor{

public cmdsmelt(main main) {
// TODO Auto-generated constructor stub
}

@Override
public boolean onCommand(CommandSender cmdsender, Command cmd, String label,
String[] args) {
Player player = (Player) cmdsender;
if(cmd.getName().equalsIgnoreCase("smelt")){
if(player.hasPermission("legendary.smelt")){
PlayerInventory pi = player.getInventory();
if(pi.getItemInHand().getType().equals(Material.COAL_ORE)){
ItemStack coal = new ItemStack(Material.COAL,pi.getItemInHand().getAmount());
pi.setItemInHand(coal);
}
if(pi.getItemInHand().getType().equals(Material.IRON_ORE)){
ItemStack iron = new ItemStack(Material.IRON_INGOT,pi.getItemInHand().getAmount());
pi.setItemInHand(iron);
}
if(pi.getItemInHand().getType().equals(Material.GOLD_ORE)){
ItemStack gold = new ItemStack(Material.GOLD_INGOT,pi.getItemInHand().getAmount());
pi.setItemInHand(gold);
}
if(pi.getItemInHand().equals(Material.LAPIS_ORE)){
ItemStack lapis = new ItemStack(Material.LAPIS_BLOCK,pi.getItemInHand().getAmount());
pi.setItemInHand(lapis);
}
if(pi.getItemInHand().getType().equals(Material.DIAMOND_ORE)){
ItemStack diamond = new ItemStack(Material.DIAMOND,pi.getItemInHand().getAmount());
pi.setItemInHand(diamond);
}
if(pi.getItemInHand().getType().equals(Material.EMERALD_ORE)){
ItemStack emerald = new ItemStack(Material.EMERALD,pi.getItemInHand().getAmount());
pi.setItemInHand(emerald);
}
if(pi.getItemInHand().getType().equals(Material.QUARTZ_ORE)){
int quartzi = pi.getItemInHand().getAmount();
ItemStack quartz = new ItemStack(Material.QUARTZ_ORE,quartzi);
pi.setItemInHand(quartz);
}
if(pi.getItemInHand().getType().equals(Material.REDSTONE_ORE)){
int redstonei = pi.getItemInHand().getAmount();
ItemStack redstone = new ItemStack(Material.REDSTONE,redstonei);
pi.setItemInHand(redstone);
}
}

}

// TODO Auto-generated method stub
return false;
}


}