JVAVBigInteger类的使用

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import java.math.*;
import java.text.DecimalFormat;
import java.util.Scanner;
public class bignum {
	public static void main(String args[]){
		BigInteger a,b;
		String s;
		char op;
		Scanner cin=new Scanner(System.in);
		while(cin.hasNext()){
			a=cin.nextBigInteger();
			s=cin.next();
			op=s.charAt(0);
			if(op == '+'){
				b=cin.nextBigInteger();
				System.out.println(a.add(b));
			}else if(op=='-'){
				b=cin.nextBigInteger();
				System.out.println(a.subtract(b));
			}else if(op=='*'){
				b=cin.nextBigInteger();
				System.out.println(a.multiply(b));
			}/*else if(op=='/'){
				b=cin.nextBigInteger();
				System.out.println(a.divide(b));
			}*/else if(op=='%'){
				b=cin.nextBigInteger();
				System.out.println(a.mod(b));
			}else{
				BigDecimal a1,b1,eps;
				String s1,s2,temp;
				s1=a.toString();
				a1=new BigDecimal(s1);
				b=cin.nextBigInteger();
				s2=b.toString();
				b1=new BigDecimal(s2);
				int c=cin.nextInt();
				eps=a1.divide(b1,c,4);
				if(c!=0){
					temp="0.";
					for(int i=0;i<c;i++) temp+="0";
					DecimalFormat gd=new DecimalFormat(temp);
					System.out.println(gd.format(eps));
				}
				else 
					System.out.println(eps);
			}
				
		}
	}
}