BankTeller.java

package thinkinginjava.generics;

// A very simple bank teller simulation.
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.Random;

import thinkinginjava.util.Generator;

class Customer {
	private static long counter = 1;
	private final long id = counter++;

	private Customer() {
	}

	public String toString() {
		return "Customer " + id;
	}

	// A method to produce Generator objects:
	public static Generator<Customer> generator() {
		return new Generator<Customer>() {
			public Customer next() {
				return new Customer();
			}
		};
	}
}

class Teller {
	private static long counter = 1;
	private final long id = counter++;

	private Teller() {
	}

	public String toString() {
		return "Teller " + id;
	}

	// A single Generator object:
	public static Generator<Teller> generator = new Generator<Teller>() {
		public Teller next() {
			return new Teller();
		}
	};
}

public class BankTeller {
	public static void serve(Teller t, Customer c) {
		System.out.println(t + " serves " + c);
	}

	public static void main(String[] args) {
		Random rand = new Random(47);
		Queue<Customer> line = new LinkedList<Customer>();
		Generators.fill(line, Customer.generator(), 15);
		
		List<Teller> tellers = new ArrayList<Teller>();
		Generators.fill(tellers, Teller.generator, 4);
		
		for (Customer c : line)
			serve(tellers.get(rand.nextInt(tellers.size())), c);
	}
}