import java.text.DecimalFormat
import java.text.DecimalFormatSymbols
/*
Program: Print numbers with a thousand separator as spaces in Kotlin.
Architecture notes:
-------------------
- Kotlin uses Java's formatting classes under the hood.
- DecimalFormat allows customizing:
* grouping separator (thousands separator)
* grouping size
- We configure DecimalFormatSymbols to use a space (' ') as the separator.
- The formatter is reused for all numbers to avoid repeated allocations.
Performance notes:
------------------
- Formatting is O(n) in the number of digits.
- DecimalFormat is efficient and safe for repeated use.
- Memory usage is minimal; only small strings are created.
Pitfalls:
---------
- DecimalFormat is not thread-safe; avoid sharing across threads without care.
- Negative numbers must preserve the minus sign; DecimalFormat handles this.
- Very large numbers (BigInteger) require converting to string first.
Security notes:
---------------
- No external input parsing; safe for demonstration.
- Avoid printing sensitive values in real systems.
Tests:
------
- Positive numbers
- Negative numbers
- Zero
- Very large integers
*/
// Create a reusable formatter with space as thousands separator
private val formatter: DecimalFormat = run {
val symbols = DecimalFormatSymbols().apply {
groupingSeparator = ' ' // use space instead of comma
}
DecimalFormat("#,###", symbols).apply {
groupingSize = 3 // group digits in threes
}
}
// Format a long value using the custom formatter
fun formatWithSpaces(value: Long): String {
return try {
formatter.format(value)
} catch (ex: Exception) {
"unformatted (error: ${ex.message})"
}
}
fun main() {
val tests: Array<Long> = arrayOf(
0,
42,
1234,
987_654_321,
-1_234_567,
1_000_000_000_000_000_000L // 10^18
)
println("Running test cases:\n")
for (n in tests) {
println("Original: $n")
println("Formatted: ${formatWithSpaces(n)}")
println()
}
}
/*
run:
Running test cases:
Original: 0
Formatted: 0
Original: 42
Formatted: 42
Original: 1234
Formatted: 1 234
Original: 987654321
Formatted: 987 654 321
Original: -1234567
Formatted: -1 234 567
Original: 1000000000000000000
Formatted: 1 000 000 000 000 000 000
*/
