How Can I Format Floating-Point Numbers to Avoid Unnecessary Trailing Zeros?

Formatting Floating-Point Numbers with Precise Control

When dealing with floating-point numbers, it's often desirable to format them aesthetically without unnecessary decimal zeros. Consider the task of printing a range of values that include integers stored as doubles and genuine doubles.

Avoiding Trailing Zeros with Specific Format Codes

While String.format("%f", value) may seem suitable, it appends trailing zeros for small values. To achieve the desired precision, consider employing alternative format codes:

Custom Formatting Function with Decimal Check

For precise control, implement a custom formatting function that differentiates between integers and doubles:

public static String fmt(double d) {
    if (d == (long) d)
        return String.format("%d", (long) d);
    else
        return String.format("%s", d);
}

This function checks if the double value represents an integer (using casting coerced to long). If it does, it formats the value as an integer using String.format("%d"); otherwise, it formats the double without unnecessary precision.

Output Example:

Using this custom function, the desired output can be achieved:

232
0.18
1237875192
4.58
0
1.2345

Note on Locale Considerations

String formatting is locale-sensitive. The precise formatting results may vary depending on regional settings.

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