关于BigDecimal常量的使用ROUND_UP,ROUND_DOWN,ROUND_HALF_UP,ROUND_HALF_DOWN

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我是靠谱客的博主苗条西装，最近开发中收集的这篇文章主要介绍关于BigDecimal常量的使用ROUND_UP,ROUND_DOWN,ROUND_HALF_UP,ROUND_HALF_DOWN，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

ROUND_UP

截断的小数>0时进一位

        //ROUND_UP
        BigDecimal zero = new BigDecimal("1.0750000");
        BigDecimal one = new BigDecimal("1.0750001");
    
        BigDecimal two = zero.setScale(3,BigDecimal.ROUND_UP);
        BigDecimal three = one.setScale(3,BigDecimal.ROUND_UP);

        System.out.println("two="+two); //two=1.075
        System.out.println("three="+three); //three=1.076

ROUND_DOWN

直接舍弃截断的小数,不在小数位上进一位,不管舍弃的数值有多大

        BigDecimal zero = new BigDecimal("1.0740000");
        BigDecimal one = new BigDecimal("1.0790001");

        BigDecimal two = zero.setScale(2,BigDecimal.ROUND_DOWN);
        BigDecimal three = one.setScale(2,BigDecimal.ROUND_DOWN);
        System.out.println("two="+two);
        System.out.println("three="+three);

        two=1.07
        three=1.07

ROUND_HALF_UP

四舍五入,数学意义上的四舍五入

        BigDecimal zero = new BigDecimal("1.0740000");
        BigDecimal one = new BigDecimal("1.0790001");

        BigDecimal two = zero.setScale(2,BigDecimal.ROUND_HALF_UP);
        BigDecimal three = one.setScale(2,BigDecimal.ROUND_HALF_UP);
        System.out.println("two="+two);
        System.out.println("three="+three);

        two=1.07
        three=1.08

ROUND_HALF_DOWN

一开始我以为这个是五舍六入,其实不是

当截取掉的小数位的值>=5,且5后面还有>0的值,就会进一位

        BigDecimal zero = new BigDecimal("1.0740001");
        BigDecimal one = new BigDecimal("1.075000");
        BigDecimal one1 = new BigDecimal("1.075001");

        BigDecimal two = zero.setScale(2,BigDecimal.ROUND_HALF_DOWN);
        BigDecimal three = one.setScale(2,BigDecimal.ROUND_HALF_DOWN);
        BigDecimal three1 = one1.setScale(2,BigDecimal.ROUND_HALF_DOWN);
        System.out.println("two="+two);
        System.out.println("three="+three);
        System.out.println("three1="+three1);

        two=1.07
        three=1.07
        three1=1.08