java的BigInteger使用指南

 1 import java.util.*;
 2 import java.math.*;
 3 
 4 public class Main{
 5     public static void main(String[] args)
 6     {
 7         BigInteger a,c,aa,cc;
 8         int b,d,ans;
 9         Scanner in=new Scanner(System.in);
10         while (in.hasNext())
11         {
12             aa=new BigInteger("1");
13             cc=new BigInteger("1");
14             a=in.nextBigInteger();
15             b=in.nextInt();
16             c=in.nextBigInteger();
17             d=in.nextInt();
18             if ((a.compareTo(c)==1)&&(b>d))
19                 ans=1;
20             else if ((a.compareTo(c)==-1)&&(b<d))
21                 ans=-1;
22             else
23             {
24                 while (b>0)
25                 {
26                     if (b%2!=0)
27                         aa=aa.multiply(a);
28                     b=b/2;
29                     a=a.multiply(a);
30                 }
31                 while (d>0)
32                 {
33                     if (d%2!=0)
34                         cc=cc.multiply(c);
35                     d=d/2;
36                     c=c.multiply(c);
37                 }
38                 
39                 //System.out.println(aa+"  "+cc);
40                 ans=aa.compareTo(cc);
41             }
42             if (ans==0)
43                 System.out.println("=");
44             else if (ans==-1)
45                 System.out.println("<");    //aa<cc
46             else if (ans==1)
47                 System.out.println(">");    //aa>cc
48         }
49     }
50 }