public class Pizza {
    private String pizzaSize;
    private String crust;
    private int cheeseCount;
    private int pepperoniCount;
    private int hamCount;
    private int mushroomsCount;
    
    public static class Builder {
        private String pizzaSize; // mandatory
        private String crust; // mandatory
        private int cheeseCount = 0; // optional
        private int pepperoniCount = 0; // optional
        private int hamCount = 0; // optional
        private int mushroomsCount = 0; // optional
        
        public Builder(String pizzaSize, String crust) {
            this.pizzaSize = pizzaSize;
            this.crust = crust;
        }
        
        public Builder cheeseCount(int cheeseCount) {
            this.cheeseCount = cheeseCount;
            return this;
        }
        
        public Builder pepperoniCount(int pepperoniCount) {
            this.pepperoniCount = pepperoniCount;
            return this;
        }
        
        public Builder hamCount(int hamCount) {
            this.hamCount = hamCount;
            return this;
        }
        
        public Builder mushroomsCount(int mushroomsCount) {
            this.mushroomsCount = mushroomsCount;
            return this;
        }
        
        public Pizza build() {
            return new Pizza(this);
        }
    }
    
    private Pizza(Builder builder) {
        this.pizzaSize = builder.pizzaSize;
        this.crust = builder.crust;
        this.cheeseCount = builder.cheeseCount;
        this.pepperoniCount = builder.pepperoniCount;
        this.hamCount = builder.hamCount;
        this.mushroomsCount = builder.mushroomsCount;
    }
    
    // getters
}