The double type in Java displays two decimals, such as 12.00

How does a double type of data retain two decimal places? Prawns, you. The existing double type of data, how to convert to a number that retains two decimal places, the type of the return value is still a double type, not a string type. For example 0, return "0.00";
Tip: DecimalFormat df = new DecimalFormat ("# # #0.00");     System.out.println (Df.format (d)); This code can be a double type of data set to retain two bits, but the return is a string type, want to return a double type, what to do?
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First you have to figure out what the model is and what is unfolding.
Since "customer demand is to be able to display 0.0 also as 0.00", then the customer did not ask that "hope 0 in the internal preservation of the time also saved as 0.00", he wanted to just show. So, no matter what you save, as long as you can show the time to turn into the format he wants.
If you want to store a 0 in the form of 0.00, then I have to tell you that only string and BigDecimal can be selected, it is absolutely impossible to simply use a double implementation.
For double, 0 and 0.00 are always the same. If you want to ask why, I can tell you, so that the number of means you will feel more in line with the concept of the number you have received, otherwise it will be a bit messy.
If you are interested, you can carefully first look at BigDecimal's Javadoc, because BigDecimal can respectively represent 0 and 0.0 and 0.00 and so on, resulting in a very strange phenomenon, that is, in the bigdecimal of the expression: 0.equals (0.0) and 0. Equals (0.00) will return false, while 0.compareTo (0.0) and 0.compareTo (0.00) will return 0. BigDecimal ratedecimal = new BigDecimal (12);//12 is a double type

BigDecimal Num=ratedecimal.setscale (1, bigdecimal.round_half_up);

Num is 12.00; use BigDecimal to help show the back 0

Round_ceiling The nearest value that is greater than or equal to the number Round_down positive number is less than or equal to the number of the nearest, negative number is greater than or equal to the number of the nearest Round_floor the value that is less than or equal to the number Round_half_down five-loft six-in Round_half_even rounds to the nearest side (distance), unless both sides (distance) are equal, if so, if the reserved bits are odd, use round_half_up, if an even number, use Round_half_down Round_half_up rounding Round_unnecessary calculation results are accurate and do not require rounding mode Round_up and Round_down opposite

The double type in Java displays two decimals, such as 12.00