java BigDecimal

package com.qjx.springbootmybatis.Test;

import java.math.BigDecimal;

/**
 * @ClassName:MTest
 * @Author:QinJinxiang
 * @Date:2018/6/27 17:56
 * @Description:TODO
 **/
public class MTest {
    public static void main(String[] args) {
        System.out.println("---------------");

        ROUND_UP();
        System.out.println("---------------");

        ROUND_DOWN();
        System.out.println("---------------");


        ROUND_CEILING();
        System.out.println("---------------");


        ROUND_FLOOR();
        System.out.println("---------------");


        ROUND_HALF_UP();
        System.out.println("---------------");


        ROUND_HALF_DOWN();
        System.out.println("---------------");


        ROUND_HALF_EVEN();
        System.out.println("---------------");


        ROUND_UNNECESSARY();
        System.out.println("---------------");


    }

    private static void ROUND_UP(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_UP);
        System.out.println("ROUND_UP -12.4444 = "+f);

    }

    private static void ROUND_DOWN(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("ROUND_DOWN -12.4444 = "+f);
    }

    private static void ROUND_CEILING(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_CEILING);
        System.out.println("ROUND_CEILING -12.4444 = "+f);
    }

    private static void ROUND_FLOOR(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_FLOOR);
        System.out.println("ROUND_FLOOR -12.4444 = "+f);
    }

    private static void ROUND_HALF_UP(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("ROUND_HALF_UP -12.4444 = "+f);
    }

    private static void ROUND_HALF_DOWN(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("ROUND_HALF_DOWN -12.4444 = "+f);
    }

    private static void ROUND_HALF_EVEN(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_HALF_EVEN);
        System.out.println("ROUND_HALF_EVEN -12.4444 = "+f);
    }

    private static void ROUND_UNNECESSARY(){
        BigDecimal a =new BigDecimal(String.valueOf(12.5555)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY 12.5555 = "+a);

        BigDecimal b =new BigDecimal(String.valueOf(12.6666)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY 12.6666 = "+b);

        BigDecimal c =new BigDecimal(String.valueOf(12.4444)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY 12.4444 = "+c);

        BigDecimal d =new BigDecimal(String.valueOf(-12.5555)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY -12.5555 = "+d);

        BigDecimal e =new BigDecimal(String.valueOf(-12.6666)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY -12.6666 = "+e);

        BigDecimal f =new BigDecimal(String.valueOf(-12.4444)).setScale(2,BigDecimal.ROUND_UNNECESSARY);
        System.out.println("ROUND_UNNECESSARY -12.4444 = "+f);
    }
    
}

運行結果： ---------------
ROUND_UP 12.5555 = 12.56
ROUND_UP 12.6666 = 12.67
ROUND_UP 12.4444 = 12.45
ROUND_UP -12.5555 = -12.56
ROUND_UP -12.6666 = -12.67
ROUND_UP -12.4444 = -12.45
---------------
ROUND_DOWN 12.5555 = 12.55
ROUND_DOWN 12.6666 = 12.66
ROUND_DOWN 12.4444 = 12.44
ROUND_DOWN -12.5555 = -12.55
ROUND_DOWN -12.6666 = -12.66
ROUND_DOWN -12.4444 = -12.44
---------------
ROUND_CEILING 12.5555 = 12.56
ROUND_CEILING 12.6666 = 12.67
ROUND_CEILING 12.4444 = 12.45
ROUND_CEILING -12.5555 = -12.55
ROUND_CEILING -12.6666 = -12.66
ROUND_CEILING -12.4444 = -12.44
---------------
ROUND_FLOOR 12.5555 = 12.55
ROUND_FLOOR 12.6666 = 12.66
ROUND_FLOOR 12.4444 = 12.44
ROUND_FLOOR -12.5555 = -12.56
ROUND_FLOOR -12.6666 = -12.67
ROUND_FLOOR -12.4444 = -12.45
---------------
ROUND_HALF_UP 12.5555 = 12.56
ROUND_HALF_UP 12.6666 = 12.67
ROUND_HALF_UP 12.4444 = 12.44
ROUND_HALF_UP -12.5555 = -12.56
ROUND_HALF_UP -12.6666 = -12.67
ROUND_HALF_UP -12.4444 = -12.44
---------------
ROUND_HALF_DOWN 12.5555 = 12.56
ROUND_HALF_DOWN 12.6666 = 12.67
ROUND_HALF_DOWN 12.4444 = 12.44
ROUND_HALF_DOWN -12.5555 = -12.56
ROUND_HALF_DOWN -12.6666 = -12.67
ROUND_HALF_DOWN -12.4444 = -12.44
---------------
ROUND_HALF_EVEN 12.5555 = 12.56
ROUND_HALF_EVEN 12.6666 = 12.67
ROUND_HALF_EVEN 12.4444 = 12.44
ROUND_HALF_EVEN -12.5555 = -12.56
ROUND_HALF_EVEN -12.6666 = -12.67
ROUND_HALF_EVEN -12.4444 = -12.44
---------------

 

 

在銀行、賬戶、計費等領域，BigDecimal提供了精確的數值計算。其中8種舍入方式值得掌握。

一、ROUND_UP

舍入遠離零的舍入模式。

在丟棄非零部分以前始終增長數字(始終對非零捨棄部分前面的數字加1)。

注意，此舍入模式始終不會減小計算值的大小。

二、ROUND_DOWN

接近零的舍入模式。

在丟棄某部分以前始終不增長數字(從不對捨棄部分前面的數字加1，即截短)。

注意，此舍入模式始終不會增長計算值的大小。

三、ROUND_CEILING

接近正無窮大的舍入模式。

若是 BigDecimal 爲正，則舍入行爲與 ROUND_UP 相同;

若是爲負，則舍入行爲與 ROUND_DOWN 相同。

注意，此舍入模式始終不會減小計算值。

四、ROUND_FLOOR

接近負無窮大的舍入模式。

若是 BigDecimal 爲正，則舍入行爲與 ROUND_DOWN 相同;

若是爲負，則舍入行爲與 ROUND_UP 相同。

注意，此舍入模式始終不會增長計算值。

五、ROUND_HALF_UP

向「最接近的」數字舍入，若是與兩個相鄰數字的距離相等，則爲向上舍入的舍入模式。

若是捨棄部分 >= 0.5，則舍入行爲與 ROUND_UP 相同;不然舍入行爲與 ROUND_DOWN 相同。

注意，這是咱們大多數人在小學時就學過的舍入模式(四捨五入)。

六、ROUND_HALF_DOWN

向「最接近的」數字舍入，若是與兩個相鄰數字的距離相等，則爲上舍入的舍入模式。

若是捨棄部分 > 0.5，則舍入行爲與 ROUND_UP 相同;不然舍入行爲與 ROUND_DOWN 相同(五舍六入)。

七、ROUND_HALF_EVEN    銀行家舍入法

向「最接近的」數字舍入，若是與兩個相鄰數字的距離相等，則向相鄰的偶數舍入。

若是捨棄部分左邊的數字爲奇數，則舍入行爲與 ROUND_HALF_UP 相同;

若是爲偶數，則舍入行爲與 ROUND_HALF_DOWN 相同。

注意，在重複進行一系列計算時，此舍入模式能夠將累加錯誤減到最小。

此舍入模式也稱爲「銀行家舍入法」，主要在美國使用。四捨六入，五分兩種狀況。

若是前一位爲奇數，則入位，不然捨去。

如下例子爲保留小數點1位，那麼這種舍入方式下的結果。

1.15>1.2 1.25>1.2

八、ROUND_UNNECESSARY

斷言請求的操做具備精確的結果，所以不須要舍入。

若是對得到精確結果的操做指定此舍入模式，則拋出ArithmeticException。

 經常使用取值四捨五入（ROUND_HALF_UP） ；

由於咱們是屬於互聯網金融行業，全部在進行計算的時候儘可能使用ROUND_HALF_EVEN    銀行家舍入法