Advanced Pie example

AdvancedPie.java

@Override
public void onEnable() {
    Metrics metrics = new Metrics(this);
    metrics.addCustomChart(new AdvancedPie("most_famous_foods", new Callable<Map<String, Integer>>() {
        @Override
        public Map<String, Integer> call() throws Exception {
            Map<String, Integer> valueMap = new HashMap<>();
            valueMap.put("Apple", getPlayersWithFood(Material.APPLE));
            valueMap.put("Bread", getPlayersWithFood(Material.BREAD));
            return valueMap;
        }
        
        private int getPlayersWithFood(Material food) {
            int counter = 0;
            for (Player player : Bukkit.getOnlinePlayers()) {
                if (player.getInventory().contains(food)) {
                    counter++;
                }
            }
            return counter;
        }
    }));
}
// If you use the Copy & Paste Metrics classes, use `Metrics.AdvancedPie` instead

This could be simplified to my knowledge by using anonymous lambda (Or what you call those)

Example:

@Override
public void onEnable() {
    Metrics metrics = new Metrics(this);
    metrics.addCustomChart(new Metrics.AdvancedPie("most_famous_foods", () -> {
        Map<String, Integer> values = new HashMap<>();
        
        values.put("Apple", getPlayersWithFood(Material.APPLE));
        values.put("Bread", getPlayersWithFood(Material.BREAD));
        
        private int getPlayersWithFood(Material food) {
            int counter = 0;
            for (Player player : Bukkit.getOnlinePlayers()) {
                if (player.getInventory().contains(food)) {
                    counter++;
                }
            }
            return counter;
        }

        return values;
    }));
}