Java精确计算，用BigDecimal来处理int、double、float等之间的计算

public static void main(String[] args) {
		BigDecimal b1 = new BigDecimal(Integer.toString(3));;
		BigDecimal b2 = new BigDecimal(Double.toString(4.9));
		System.out.println(b1);
		System.out.println(b2);
		System.out.println(b1.multiply(b2));
	}