待解：用二进制形式显示任何整数的二进制值

 1 package com.java7.showbitsdemo;
 2 /*
 3  * Try This 5-3
 4  * A class that displays the binary representation of a value.
 5  */
 6 class ShowBits {
 7     int numbits;
 8     
 9     ShowBits(int n) {
10         numbits = n;
11     }
12     
13     void show(long val) {
14         long mask = 1;
15         
16         // left-shift a 1 into the proper position
17         mask <<= numbits-1;
18         
19         int spacer = 0;
20         for(; mask != 0; mask >>>=1) {
21             if((val & mask) != 0) System.out.print("1");
22             else System.out.print("0");
23             spacer++;
24             if((spacer % 8) == 0) {
25                 System.out.print("");
26                 spacer = 0;
27             }
28         }
29         System.out.println();
30     }
31 }
32 
33 // Demonstrate ShowBits.
34 class ShowBitsDemo {
35     public static void main(String[] args) {
36         ShowBits b = new ShowBits(8);
37         ShowBits i = new ShowBits(32);
38         ShowBits li = new ShowBits(64);
39         System.out.println("123 in binary: ");
40         b.show(123);
41         
42         System.out.println("\n87987 in binary: ");
43         i.show(87987);
44         
45         System.out.println("\n237658768 in binary: ");
46         li.show(237658768);
47         
48         // you can also show low-order bits of any integer
49         System.out.println("\nLow order 8 bits of 87987 in binary: ");
50         b.show(87987);
51     }
52 }