double類型數相除保留兩位小數

參考文章：

https://www.cnblogs.com/wangpei/p/4756055.html

https://blog.csdn.net/dongapple/article/details/76974624

 

一、需要使用BigDecimal來實現

package com.cy.test.math;

import java.math.BigDecimal;

public class TestJiSuan {

    public static void main(String[] args) {
        double a = 1;
        double b = 3;
        double c = a / b;
        System.out.println(c);                          //0.3333333333333333
        System.out.println(divide(a, b, 2));      //0.33

        int total = 21;
        int count = 9;
        double average = total / count;                 
        System.out.println(average);                    //2.0
        System.out.println((double)total);              //21.0
        System.out.println(divide((double)total, (double)count, 2)); //2.33
    }

    /**
     * 兩個double類型的數相除，保留兩位小數
     * @param a
     * @param b
     * @param scale
     * @return
     */
    public static double divide(double a, double b, int scale){
        BigDecimal bd1 = new BigDecimal(Double.toString(a));
        BigDecimal bd2 = new BigDecimal(Double.toString(b));
        return bd1.divide(bd2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
    }
}

 

二、DecimalFormat

參考文章：https://www.jb51.net/article/135720.htm

/**
     * 計算結果百分比，保留1位小數
     *
     * @param a 除數
     * @param b 被除數
     * @return
     */
    private static String calculateResultOfPercent(Integer a, Integer b) {
        if (b == 0) {
            return "0%";
        }

        DecimalFormat df = new DecimalFormat("#.#%");
        return df.format((double) a / b);
    }

 

 

 

 

 

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