try expression

Learn to use try as an expression in Kotlin.

try as an expression: returns a value

In Kotlin try is an expression; it yields a value. The catch block can also return a value; that lets you give a fallback.

val n = try {
    "42".toInt()
} catch (e: NumberFormatException) {
    0
}
// n = 42

On success the last line of the try block, on error the last line of the catch block is the result. This builds a flow similar to if/else. The result can be assigned directly to a variable.

Nullable results in try expressions

If the catch block returns null, the result may be null. The variable then becomes nullable; safe access is needed.

val n: Int? = try {
    "abc".toInt()
} catch (e: NumberFormatException) {
    null
}
println(n ?: -1)  // -1

The Elvis operator ?: gives a fallback for a null value. This lets you handle nullable results safely. This approach makes it easy to silently fall back when a conversion fails.

Exercise Convert a string to a number

With a try expression, call "42".toInt(); catch NumberFormatException and return 0. Assign the result to val n and print it with println.

Show example solution

fun main() {
    val n = try {
        "42".toInt()
    } catch (e: NumberFormatException) {
        0
    }
    println(n)
}

Test yourself

What does `val n = try { x.toInt() } catch (e) { 0 }` do?
- It writes 0 to n
- It writes null to n
- It writes the try value to n
- It gives a compile error
Show answer

It writes the try value to n — On no error the try value, on error the catch 0 goes to n.

Fill in the blank: try expression

val n = ____ { "42".toInt() } catch (e: NumberFormatException) { 0 }

Show answer

val n = try { "42".toInt() } catch (e: NumberFormatException) { 0 }

Match part to role

try { }

Trial
catch { }

Fallback value
val n =

Assignment
.toInt()

Conversion

Next lesson: Custom exceptions

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