java中2個或多個數字變量直接相乘相加減運算

利用Double.valueOf(str)將str轉為double 類型，2個數即可直接相乘、相加減運算

String a="24.3";

String b="3";

double addResult=Double.valueOf(a)+Double.valueOf(b);

double jianResult=Double.valueOf(a)-Double.valueOf(b);

double mutiResult=Double.valueOf(a)*Double.valueOf(b);

BigDecimal c=new BigDecimal(mutiResult);