使用泛型來建立匿名類
阿新 • • 發佈:2018-12-26
interface Generator<T> { T next(); } class Generators{ public static <T> Collection<T> fill(Collection<T> coll, Generator<T> gen, int n){ for(int i = 0; i < n; i++){ coll.add(gen.next()); } return coll; } } class Customer{ private static long counter = 1; private final long id = counter++; //構造器private 不能直接建立物件 private Customer(){} public String toString(){ return "Customer "+ id;} public static Generator<Customer> generator(){ return new Generator<Customer>() { @Override 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; } public static Generator<Teller> generator(){ return new Generator<Teller>() { @Override public Teller next() { return new Teller(); } }; } } public class Main{ public static void serve(Teller t, Customer c){ System.out.println(t + " serves" + c ); } public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException { //Teller t = new Teller(); //沒有public構造方法 Random rand = new Random(47); Queue<Customer> line = new LinkedList<Customer>(); Generators.fill(line, Customer.generator(), 8); List<Teller> tellers = new ArrayList<Teller>(); Generators.fill(tellers, Teller.generator(), 4); for(Customer c : line){ serve(tellers.get(rand.nextInt(tellers.size())), c); } } }
執行結果:
Teller 3 servesCustomer 1
Teller 2 servesCustomer 2
Teller 3 servesCustomer 3
Teller 1 servesCustomer 4
Teller 1 servesCustomer 5
Teller 3 servesCustomer 6
Teller 1 servesCustomer 7
Teller 2 servesCustomer 8