双Java取整

Question

public class project3 {
    public static void main(String[] args) {

        int earnedRuns = 52;
        int inningsPitched = 182;
        double ERA = (earnedRuns * 9) / inningsPitched;
        String FirstName = "Anibal";
        String LastName = "Sanchez";

        System.out.println("Pitcher's first name: " + FirstName);
        System.out.println("Pitcher's last name: " + LastName);
        System.out.println("Number of earned runs: " + earnedRuns);
        System.out.println("Number of innings pitched: " + inningsPitched);
        System.out.println(FirstName + " " + LastName + " has an ERA of " + ERA);
    }
}

ERA的结果是2.0而不是2.57 ...我无法弄清楚为什么

Answer 1

从根本上讲，您是：

1. 将整数乘以整数 -> 整数 （结果：486）
2. 将整数除以整数 -> 整数 （结果：2）
3. 将结果分配给double变量 -> double （结果：2.0D）

所以，你首先需要投 （“转换”）的整数浮点或双精度。

double ERA = ((double)earnedRuns * 9) / inningsPitched;

或更简单：

double ERA = (earnedRuns * 9.0) / inningsPitched;

仅强制转换一个整数就足够了，因为在Java中：integer * double-> double

编辑：

9.0 D或9.0 d只是告诉java 9.0是一个double 。 同样适用于9.0 f或9.0 F。 这意味着9.0是float 。