运用JAVA中大数类实现大数的四则运算

public static void main(String[] args) {
// TODO Auto-generated method stub
BigInteger aa =new BigInteger("100");
BigInteger bb= new BigInteger("25");
BigInteger sub=aa.subtract(bb);//大整数的减
BigInteger add=aa.add(bb);//大整数的加
BigInteger mul=aa.multiply(bb);//大整数的乘
BigInteger div=aa.divide(bb);//大整数的除
System.out.println(sub.toString());
System.out.println(add.toString());
System.out.println(mul.toString());
System.out.println(div.toString());
}

import java.math.BigInteger;

public class BigIntegerGet {
public String getAdd(String Str1,String Str2){
String Str3=new String();
BigInteger BigInt1=new BigInteger(Str1);
BigInteger BigInt2=new BigInteger(Str2);
BigInt1=BigInt1.add(BigInt2);
Str3=BigInt1.toString();
return Str3;
}
public String getSubtract(String Str1,Strin