Java泛型(2)：泛型接口

泛型不仅可以在类上实现，也可以在接口上实现。JDK中[Iterable<T> <-- Collection<E> <-- List<E>/Queue<E>/Set<E>]都是泛型接口。

下面是一个泛型接口的例子。这是一个一个生成器的例子。生成器用来专门创建对象。这是工厂方法设计模式的一种应用。一般来说生成器只有一个用来生成新的对象的方法。

 public interface Generator<T> {
     T next();
     boolean hasNext();
 }

 public class CoffeeGenerator implements Generator<Coffee> {

     private int[] numList;

     private int pos;

     public CoffeeGenerator(int[] numList) {
         this.numList = numList;
         pos = 0;
     }

     @Override
     public Coffee next() {
         switch (numList[pos++]) {
         case Cappuccino.NUM:
             return new Cappuccino();
         case Latte.NUM:
             return new Latte();
         case Mocha.NUM:
             return new Mocha();
         default:
             return null;
         }
     }

     @Override
     public boolean hasNext() {
         return numList != null && numList.length != 0 && numList.length > pos;
     }
 }

 public interface Coffee {
     int getPrice();
     void make();
 }

 public class Cappuccino implements Coffee {

     public final static int NUM = 1;

     Cappuccino() {
         make();
     }

     @Override
     public int getPrice() {
         return 38;
     }

     @Override
     public void make() {
         System.out.println("Making " + getClass().getSimpleName() + "...");
     }
 }

 public class Latte implements Coffee {

     public final static int NUM = 2;

     Latte() {
         make();
     }

     @Override
     public int getPrice() {
         return 32;
     }

     @Override
     public void make() {
         System.out.println("Making " + getClass().getSimpleName() + "...");
     }
 }

 public class Mocha implements Coffee {

     public final static int NUM = 3;

     Mocha() {
         make();
     }

     @Override
     public int getPrice() {
         return 35;
     }

     @Override
     public void make() {
         System.out.println("Making " + getClass().getSimpleName() + "...");
     }
 }

Main方法测试：

         Generator<Coffee> coffeeGen = new CoffeeGenerator(new int[] { 1, 3, 2, 1, 1, 3 });
         int totalPrice = 0;
         while (coffeeGen.hasNext()) {
             Coffee coffee = coffeeGen.next();
             totalPrice += coffee.getPrice(); // Making Cappuccino/Mocha/Latte/Cappuccino/Cappuccino/Mocha...
         }
         System.out.println(totalPrice); //