Question

java double 相加问题

double b1 = 31.4565d + 0.0001d;
System.out.println(b1);
double b2 = 0.0001;
double db = 31.4565 + b2;
System.out.println(db);
一开始输出b1得到31.4565 后来输出b2 以后 b1 和b2都输出 31.456599999999998

怎么才能正确相加呢

Answer 1

NumberFormat nf = NumberFormat.getInstance ();
System.out.println (nf.format (db));

追问

不对啊 我输出是31.457

应该是 31.4566才对啊

追答

DecimalFormat df = new DecimalFormat ("#.####");
System.out.println (df.format (db));