Changing a decimal format within the entire code using an option created in a switch menu

问题

When writing the code, one of the tasks was to allow the user to change the decimal format within the entire program.

The program consists of multiple calculators, all of them should be able to give decimal results. The user has then a choice of how many decimal places they would like to see.

I know this can be done with format options just not sure how.

/Answer given already

回答1:

Create a variable containing a DecimalFormat

DecimalFormat df = new DecimalFormat();

In menu option 4 where number of decimals is selected and read into dec

df.setMaximumFractionDigits(dec);
df.setMinimumFractionDigits(dec);

The above means that numbers will always be printed with dec number of decimals

Then whenever you want to print a double use the formatter

 System.out.println("The result is " + df.format(someValue));

An example

DecimalFormat df = new DecimalFormat();
for (int i = 0; i < 4; i++) {
    df.setMaximumFractionDigits(i);
    df.setMinimumFractionDigits(i);
    System.out.println("example " + df.format(24) + " " + df.format(12.3456));
}

outputs

example 24 12
example 24.0 12.3
example 24.00 12.35
example 24.000 12.346

回答2:

Try java method: String.format();

double number = 12.43544545;
int decimalPoint = 3;

System.out.println(String.format("%." + decimalPoint + "f", number));

来源：https://stackoverflow.com/questions/54402352/changing-a-decimal-format-within-the-entire-code-using-an-option-created-in-a-sw