Java random number between 0 and 0.06

问题:

In Java, I need to randomly generate a number between 0 and 0.06.

I saw on another question on here that the following code would do the trick:

Random generator = new Random();
double number = generator.nextDouble() * .06;

However, doing that gives me really long numbers like 0.007044013589130205 and 0.03656588431980957, which I don't think is what my instructor is looking for.

Is there anyway to generate random numbers between 0 and 0.06 that only have two or three decimal places?

回答1:

You can do it this way, if you want you number to range between [0;0.06] with 0.01 of difference:

Random generator = new Random();
int number = generator.nextInt(7);
double result = number / 100.0;

You can generalize the formula number = generator.nextInt(max + 1 -min) + min; where max will be the biggest number that you what to generate and min the lowest. This will generate number from [min to max+1]

To increase the decimal places you just have to divide number for 1000, 10000 and so on.

回答2:

Internally, Java double values are a binary floating point representation. They don't have decimal places. You can format a double as a base-10 number string having a specified number of decimal places. For example, to get three decimals (precision 0.001), you could use:

String formatted = String.format("%.3f", number);

If you don't need to do any calculations with the number and you want two or three decimal places, just print 0.0 and then a two-digit random integer between 00 and 60 (inclusive).

回答3:

I assume you need precision to be 0.001, so try this:

    Random r = new Random();
    int ret = r.nextInt(60 + 1);
    return ret / 1000.0;

this will generate [0,0.060] averagely with difference multiple of 0.001,that may be your want

回答4:

Since you're dealing with sales tax, you should be aware of Why not use Double or Float to represent currency? and Using BigDecimal to work with currencies

To generate a random BigDecimal with constraints on range and # of significant digits, see How can I create a random BigDecimal in Java?