Numbers

Integer Types and Their Limits

Example

Each integer type has a minimum and maximum value. Whole numbers default to Int; add L for Long.

fun main() {
    println("Byte:  ${Byte.MIN_VALUE} to ${Byte.MAX_VALUE}")
    println("Short: ${Short.MIN_VALUE} to ${Short.MAX_VALUE}")
    println("Int:   ${Int.MIN_VALUE} to ${Int.MAX_VALUE}")
    println("Long:  ${Long.MIN_VALUE} to ${Long.MAX_VALUE}")

    val views = 3_000_000_000      // too big for Int, so inferred as Long
    println(views::class.simpleName)
}

Output

Byte:  -128 to 127
Short: -32768 to 32767
Int:   -2147483648 to 2147483647
Long:  -9223372036854775808 to 9223372036854775807
Long

Overflow

Example

Going past Int.MAX_VALUE silently wraps around to a negative number. Use Long for big values such as amounts in paise, view counts or timestamps.

fun main() {
    val max = Int.MAX_VALUE
    println(max + 1)               // wraps around!
    println(max.toLong() + 1)      // correct with Long
}

Output

-2147483648
2147483648

Floating-Point Numbers

Example

Decimal numbers default to Double (about 15–16 digits). Float needs an f suffix and keeps about 6–7 digits.

fun main() {
    val d = 10.0 / 3
    val f = 10f / 3
    println(d)
    println(f)
    println(0.1 + 0.2)     // binary floating point is not exact
    println(10 / 3)        // Int / Int = Int (decimals dropped)
    println(10 / 3.0)      // one Double makes the result Double
}

Output

3.3333333333333335
3.3333333
0.30000000000000004
3
3.3333333333333335

Tip: Never use Double for money in real apps: 0.1 + 0.2 is not exactly 0.3. Store amounts as Long paise (₹ 12.50 = 1250) or use BigDecimal. Payment apps like PhonePe and Paytm do exactly this.

Literals

Example

Underscores make big numbers readable. Hex and binary literals are also supported.

fun main() {
    val oneCrore = 1_00_00_000
    val color = 0xFF6200EE        // hex (Android colors), a Long here
    val flags = 0b1010            // binary
    println(oneCrore)
    println(color)
    println(flags)
    println(1.5e3)                // scientific notation
}

Output