Java每日解惑

 1 package jinlai.ding.com.javajiehuo;
 2
 3 import java.math.BigDecimal;
 4
 5 public class IsOld {
 6
 7     /**
 8      * 判断奇数（（计算一个数字是否奇数））
 9      * @param args
10      */
11     public static void main(String[] args) {
12         //谜题1：奇数性
13         System.out.println(isOld(-3));
14         System.out.println(isOldYes(-3));
15         //谜题2:找零时刻
16         System.out.println(2.00 - 1.10);
17         System.out.println((200 - 110) + "cents");
18         System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.10")));
19         //谜题3：长整数
20         System.out.println(longDivision());
21         System.out.println(longDivisionL());
22         //谜题4：初级问题
23         System.out.println(12345 + 54321);
24         System.out.println(12345 + 5432l);
25         System.out.println(12345 + 5432L);
26         //谜题5：十六进制的趣事
27         System.out.println(Long.toHexString(0x100000000L + 0xcafebabe));
28         System.out.println(Long.toHexString(0x100000000L + 0xcafebabeL));
29
30     }
31
32     /**
33      * 错误的判断方法
34      * @param i
35      * @return
36      */
37     public static boolean isOld(int i){
38         return i % 2 ==1;
39     }
40
41     /**
42      * 正确的判断方法
43      * @param i
44      * @return
45      */
46     public static boolean isOldYes(int i){
47         return (i & 1) != 0;
48     }
49     /**
50      * 微妙除以毫秒 溢出计算
51      * @return
52      */
53     public static long longDivision(){
54         final long MICROS_PER_DAY = 24 * 60 * 60 * 1000 * 1000;
55         final long MILLIS_PER_DAY = 24 * 60 * 60 * 1000;
56         return MICROS_PER_DAY / MILLIS_PER_DAY;
57     }
58     /**
59      * 微妙除以毫秒 不溢出计算
60      * @return
61      */
62     public static long longDivisionL(){
63         final long MICROS_PER_DAY = 24L * 60 * 60 * 1000 * 1000;
64         final long MILLIS_PER_DAY = 24L * 60 * 60 * 1000;
65         return MICROS_PER_DAY / MILLIS_PER_DAY;
66     }
67
68 }