1.?BigDecimal num1 = new BigDecimal(2.225667);//这种写法不允许,会造成精度损失
2.?BigDecimal num2 = new BigDecimal(2);//这种写法是可以的
3.?BigDecimal num = new BigDecimal("2.225667");//一般都会这样写最好
4.?int count = num.scale();
? ??? ??System.out.println(count);//6 返回的是小数点后位数
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好了,下面开始正式介绍知识点啦~~~~~~
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1.?ROUND_DOWN
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BigDecimal b =
new BigDecimal("2.225667").setScale(2,BigDecimal.ROUND_DOWN);
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2.?ROUND_UP
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BigDecimal c =
new BigDecimal("2.224667").setScale(2,BigDecimal.ROUND_UP);
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3.?ROUND_CEILING
天花板(向上),正数进位向上,负数舍位向上
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BigDecimal f =
new BigDecimal("2.224667").setScale(2,BigDecimal.ROUND_CEILING);
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BigDecimal g =
new BigDecimal("-2.225667").setScale(2,BigDecimal.ROUND_CEILING);
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4.?ROUND_FLOOR
地板(向下),正数舍位向下,负数进位向下
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BigDecimal h =
new BigDecimal("2.225667").setScale(2,BigDecimal.ROUND_FLOOR);
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BigDecimal i =
new BigDecimal("-2.224667").setScale(2,BigDecimal.ROUND_FLOOR);
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5.?ROUND_HALF_UP
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BigDecimal d =
new BigDecimal("2.225").setScale(2,BigDecimal.ROUND_HALF_UP);
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System.out.println(
"ROUND_HALF_UP"+d);
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6.?ROUND_HALF_DOWN
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BigDecimal e =
new BigDecimal("2.225").setScale(2,BigDecimal.ROUND_HALF_DOWN);
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System.out.println(
"ROUND_HALF_DOWN"+e);
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7.?ROUND_HALF_EVEN
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BigDecimal j =
new BigDecimal("2.225").setScale(2,BigDecimal.ROUND_HALF_EVEN);
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BigDecimal k =
new BigDecimal("2.215").setScale(2,BigDecimal.ROUND_HALF_EVEN);
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System.out.println(
"************************************");
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System.out.println(
"4.05: "+new BigDecimal("4.05").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.15: "+new BigDecimal("4.15").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.25: "+new BigDecimal("4.25").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.35: "+new BigDecimal("4.35").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.45: "+new BigDecimal("4.45").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.55: "+new BigDecimal("4.55").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"4.65: "+new BigDecimal("4.65").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.05: "+new BigDecimal("3.05").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.15: "+new BigDecimal("3.15").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.25: "+new BigDecimal("3.25").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.35: "+new BigDecimal("3.35").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.45: "+new BigDecimal("3.45").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.55: "+new BigDecimal("3.55").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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System.out.println(
"3.65: "+new BigDecimal("3.65").setScale(1,BigDecimal.ROUND_HALF_EVEN));
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8.ROUND_UNNECESSARY
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BigDecimal l =
new BigDecimal("2.215").setScale(3,BigDecimal.ROUND_UNNECESSARY);
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