四捨五入在我的最終輸出小數

Question

我的代碼如下：

import java.util.Scanner; 

public class AreaHexagon { 
public static void main(String[] args) { 
     Scanner s = new Scanner(System.in); 
     double side, area; 

     System.out.print("Enter the side:"); 
     side = s.nextDouble(); 

     area = ((3 * Math.pow(3, 0.5)/2)) * Math.pow(side, 2); 

     System.out.print("The area of the hexagon is " + area); 
    } 

}

我收到錯誤消息稱：6.6作爲邊長的答案應該是113.17，但我我得到113.17219976等等。我嘗試添加double roundOff = Math.round（side * 100）/ 100;但我無法讓它正常工作。

Answer 1

使用此：System.out.printf("The area of the hexagon is %.2f", area);

Answer 2

爲了減少一些小數部分，你可以使用

System.out.printf("%.2f", area); 

道歉，我已經重複我寫我自己的函數，它被切割的小數部分在指定的應答位置：

public static double cutDecimalPart(double number, int position) { 
    int power = (int) Math.pow(10, position); 
    int big = (int) (number * power); 
    return (double) big/power; 
} 

Answer 3

import java.util.Scanner; 

public class Hexagon { 
    public static void main(String[] args) { 
     Scanner s = new Scanner(System.in); 
     double side, area; 

     System.out.print("Enter the side:"); 
     side = s.nextDouble(); 




     area = ((3.0 * Math.pow(3.0, 0.5)/2.0)) * Math.pow(side, 2.0); 

     System.out.printf("The area of the hexagon is %.2f", area); 

    } 

}

這是固定的代碼，它運行平穩。感謝您的幫助@ alex-chermenin & @ wojciech-kazior