详解
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;
public class Main {
public static Scanner cin = new Scanner(System.in);
public static void main(String[] args) {
BigDecimal a = new BigDecimal("4.51");
BigDecimal b = new BigDecimal("1.5");
System.out.println("a + b =" + a.add(b));
System.out.println("a - b =" + a.subtract(b));
System.out.println("a * b =" + a.multiply(b));
//下面的不能整除，会报错，可以指定保留小数即可
// System.out.println("a / b =" + a.divide(b));
//第二个参数表示小数点后保留位数
System.out.println("a / b =" + a.divide(b,1));
System.out.println("a / b =" + a.divide(b,2));
}
}