问题描述
我最近正在使用数字，我有一种情况，我希望将双精度值的精度设置为6位数或4位数，具体取决于数据库中存储的值。
I was working with numbers recently and I had a situation where I want to set the precision of a double value say to 6 digits or 4 digits, depending on the value stored in the database.
例如，如果在数据库中精度设置为4位，则输出必须为，
For example, If in the database the precision is set as 4 digits then the output must look as,
10.0000 。
我尝试使用 DecimalFormat 并使用字符串 ##。#### ，但每次使用符号都很烦人。
I tried with DecimalFormat and using the string ##.####, but it is annoying to use symbols everytime.
有没有更好的方法，如下所示：
Is there any better approach, say something like below:
Double value = 10.0;
value.setPrecision(4);
推荐答案
您无法设置双精度（或Double）到指定的十进制数字，因为浮点值没有十进制数字。它们具有二进制数字。
You can't set the precision of a double (or Double) to a specified number of decimal digits, because floating-point values don't have decimal digits. They have binary digits.
您必须通过 BigDecimal 或<$ c转换为十进制基数$ c> DecimalFormat ，具体取决于您稍后要对该值执行的操作。
You will have to convert into a decimal radix, either via BigDecimal or DecimalFormat, depending on what you want to do with the value later.
另请参阅我对对于不可避免的反驳* 100/100答案。
See also my answer to this question for a refutation of the inevitable *100/100 answers.
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