An explicit cast to `double`

like this isn't necessary:

```
double trans = (double) trackBar1.Value / 5000.0;
```

Identifying the constant as `5000.0`

(or as `5000d`

) is sufficient:

```
double trans = trackBar1.Value / 5000.0;
double trans = trackBar1.Value / 5000d;
```

Use `setRoundingMode`

, set the `RoundingMode`

explicitly to handle your issue with the half-even round, then use the format pattern for your required output.

Example:

```
DecimalFormat df = new DecimalFormat("#.####");
df.setRoundingMode(RoundingMode.CEILING);
for (Number n : Arrays.asList(12, 123.12345, 0.23, 0.1, 2341234.212431324)) {
Double d = n.doubleValue();
System.out.println(df.format(d));
}
```

gives the output:

```
12
123.1235
0.23
0.1
2341234.2125
```

**EDIT**: The original answer does not address the accuracy of the double values. That is fine if you don't care much whether it rounds up or down. But if you want accurate rounding, then you need to take the expected accuracy of the values into account. Floating point values have a binary representation internally. That means that a value like 2.7735 does not actually have that exact value internally. It can be slightly larger or slightly smaller. If the internal value is slightly smaller, then it will not round up to 2.7740. To remedy that situation, you need to be aware of the accuracy of the values that you are working with, and add or subtract that value before rounding. For example, when you know that your values are accurate up to 6 digits, then to round half-way values up, add that accuracy to the value:

```
Double d = n.doubleValue() + 1e-6;
```

To round down, subtract the accuracy.

## Best Solution

For money,

alwaysdecimal. It's why it was created.If numbers must add up correctly or balance, use decimal. This includes any financial storage or calculations, scores, or other numbers that people might do by hand.

If the exact value of numbers is not important, use double for speed. This includes graphics, physics or other physical sciences computations where there is already a "number of significant digits".