Solved HashMap Not Storing Locations

I'm creating a cobblestone square 10x10, then when the player moves their head, it removes the previous square and places the new one where that player is looking. So it will create a square block following where they are looking.

The problem is it's not restoring the previous square, I have the following hashmap and method

Code:java

HashMap<Material, Location> trailLocations = new HashMap<Material, Location>();

Code:java

@SuppressWarnings("deprecation")
public void startTrail(String planType, Player player){
 
restorePreviousTrail();
 
Location centerLocation = player.getTargetBlock(null, 30).getLocation();
int tierMultiplyer = 2*(mainClass.getConfig().getInt(savedTownName + ".Buildings." + planType + ".Level"));
Location startDrawLocation = new Location(centerLocation.getWorld(),
centerLocation.getX()-tierMultiplyer,
centerLocation.getY(),
centerLocation.getZ()-tierMultiplyer
);
Location stopDrawLocation = new Location(centerLocation.getWorld(),
centerLocation.getX()+tierMultiplyer,
centerLocation.getY(),
centerLocation.getZ()+tierMultiplyer
);
for(double x = startDrawLocation.getX(); x <= stopDrawLocation.getX(); x++){
for(double z = startDrawLocation.getZ(); z <= stopDrawLocation.getZ(); z++){
Location l = new Location(centerLocation.getWorld(),
x,
centerLocation.getY(),
z
);
trailLocations.put(l.getBlock().getType(), l);
l.getBlock().setType(Material.COBBLESTONE);
}
}
}

That generates the new square and restores the previous one by calling this method

Code:java

private void restorePreviousTrail(){
System.out.println(trailLocations.size());
for (Map.Entry<Material, Location> entry : trailLocations.entrySet()) {
Location location = entry.getValue();
Material material = entry.getKey();
location.getBlock().setType(Material.DIAMOND_BLOCK);
}
trailLocations.clear();
}

Solved this cleared up my problem https://forums.bukkit.org/threads/tutorial-block-restoration.228896/