王浩祥 静态嵌套类(Static Nested Class)和内部类（Inner Class）的不同？

Static Nested Class是被声明为静态（static）的内部类，它可以不依赖于外部类实例被实例化。而通常的内部类需要在外部类实例化后才能实例化，其语法看起来挺诡异的，如下所示。

/**

 * 扑克类（一副扑克）

 * @author 骆昊

 *

 */

public class Poker {

    private static String[] suites = {"黑桃", "红桃", "草花", "方块"};

    private static int[] faces = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};

 

    private Card[] cards;

 

    /**

     * 构造器

     *

     */

    public Poker() {

        cards = new Card[52];

        for(int i = 0; i < suites.length; i++) {

            for(int j = 0; j < faces.length; j++) {

                cards[i * 13 + j] = new Card(suites[i], faces[j]);

            }

        }

    }

 

    /**

     * 洗牌 （随机乱序）

     *

     */

    public void shuffle() {

        for(int i = 0, len = cards.length; i < len; i++) {

            int index = (int) (Math.random() * len);

            Card temp = cards[index];

            cards[index] = cards[i];

            cards[i] = temp;

        }

    }

 

    /**

     * 发牌

     * @param index 发牌的位置

     *

     */

    public Card deal(int index) {

        return cards[index];

    }

 

    /**

     * 卡片类（一张扑克）

     * [内部类]

     * @author 骆昊

     *

     */

    public class Card {

        private String suite;   // 花色

        private int face;       // 点数

 

        public Card(String suite, int face) {

            this.suite = suite;

            this.face = face;

        }

 

        @Override

        public String toString() {

            String faceStr = "";

            switch(face) {

            case 1: faceStr = "A"; break;

            case 11: faceStr = "J"; break;

            case 12: faceStr = "Q"; break;

            case 13: faceStr = "K"; break;

            default: faceStr = String.valueOf(face);

            }

            return suite + faceStr;

        }

    }

}

测试代码：

class PokerTest {       public static void main(String[] args) {         Poker poker = new Poker();         poker.shuffle();                // 洗牌         Poker.Card c1 = poker.deal(0);  // 发第一张牌         // 对于非静态内部类Card         // 只有通过其外部类Poker对象才能创建Card对象         Poker.Card c2 = poker.new Card("红心", 1);    // 自己创建一张牌           System.out.println(c1);     // 洗牌后的第一张         System.out.println(c2);     // 打印: 红心A     } }