public class DES {
// 声明常量字节数组
private static final int[] IP = {
58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54,
46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33,
25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21,
13, 5, 63, 55, 47, 39, 31, 23, 15, 7
}; // 64
private static final int[] IP_1 = {
40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6,
46, 14, 54, 22, 62, 30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12,
52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42, 10, 50, 18,
58, 26, 33, 1, 41, 9, 49, 17, 57, 25
}; // 64
private static final int[] PC_1 = {
57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51,
43, 35, 27, 19, 11, 3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7,
62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20,
12, 4
}; // 56
private static final int[] PC_2 = {
由于常见的单例模式,饿汉式单例和懒汉式单例,构造方法都私有了,因此不能被继承.
最近在开发中遇到问题了,恰好需要继承单例类.找资料才找到了这个解决办法---登记式单例.
登记式单例类是为了克服饿汉式单例类及懒汉式单例类均不可继承的缺点而设计的。当单例类需要被继承时适用.
代码清单3：登记式单例类
import java.u ......
