java中实现进制转换

int M = in.nextInt();
int N = in.nextInt();
String num = in.next();
BigInteger mScale = new BigInteger(num,M);//以M进制构造BigInteger类型，默认不填M是10进制
System.out.println(mScale.toString(N));//把数转换为N进制。默认不填N是10进制