Checking Amount of items and getting top 3 players.

Iterate through all online players, get their inventories, iterate through their inventories, check if the ItemStack is gold, increment an integer representing their gold, etc.

 

I am sure you can figure it out yourself. Here is everything you need that is Bukkit related.
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/inventory/Inventory.html
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/inventory/ItemStack.html
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/Material.html
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/Bukkit.html

 

Hint & Neat help:
BEWARE OF THIS THING! You need a != null check

Code (Text):

PlayerInventory inventory = player.getInventory();
for (ItemStack itemstack : inventory.getContents()){
    if (itemstack != null){
        //do more stuff here
    }
}
 

More help:

Code (Text):

if (itemstack.getType() == Material.GOLD_INGOT)
 

 

There is no method to get the top three players with the most gold. You are going to have to write that yourself. You can find the methods you need here.
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/Bukkit.html
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/entity/Player.html

 

1 - get amount of gold in the player inventory
2 - store it in a hashmap
3 - sort the hashmap by value

 

Code (Java):

                for (Player all : Bukkit.getOnlinePlayers()) {
                    PlayerInventory i = all.getInventory();
                    for (ItemStack items : i.getContents()) {
                        if (items != null) {
                            if (items.getType() == Material.GOLD_INGOT) {
                                ArrayList<Integer> numbers = new ArrayList<Integer>();
                                numbers.add(items.getAmount());
                               // Fetch the 3 highest integers from the ArrayList.
                            }
                        }
                    }
                }

 

I'll just say the following and you should catch your mistake.

Code (Text):

  ArrayList<Integer> numbers =new ArrayList<Integer>();