skydoves

Function1<Integer, Integer> lambda = new Function1<Integer, Integer>() {
    @Override
    public Integer invoke(Integer it) {
        return it * 2;
    }
};
int result = higherOrderExample(lambda);

skydoves

val result = higherOrderExample { it * 2 }

skydoves

int higherOrderExample(Function1<Integer, Integer> operation) {
    return operation.invoke(10);
}

skydoves

fun higherOrderExample(operation: (Int) -> Int): Int {
    return operation(10)
}

skydoves

val id1: Any = UserId("abc")         // Stored as Any, forces boxing
val id2: UserId? = UserId("def")     // Nullable type can force boxing
val listOfIds = listOf(UserId("1"))  // Generic collection, forces boxing

skydoves

public final class IdKt {
    // The function takes the PRIMITIVE type directly
    public static final void processId(String userId) {
        String var1 = "Processing user with ID: " + userId;
        System.out.println(var1);
    }

    public static final void main() {
        // No UserId object allocated
        String myId = UserId.constructor_impl("user-123");

skydoves

@JvmInline
value class UserId(val id: String)

fun processId(userId: UserId) {
    println("Processing user with ID: ${userId.id}")
}

fun main() {
    val myId = UserId("user-123")
    processId(myId)

skydoves

// simplified
override val value: T
    get() {
        if (_value !== UNINITIALIZED_VALUE) {
            return _value as T
        }
        val initializerValue = initializer
        if (initializerValue != null) {
            val newValue = initializerValue()
            if (valueUpdater.compareAndSet(this, UNINITIALIZED_VALUE, newValue)) {

skydoves

// simplified
override val value: T
    get() {
        if (_value !== UNINITIALIZED_VALUE) {
            return _value as T // Fast path: no lock needed
        }
        return synchronized(lock) {
            if (_value !== UNINITIALIZED_VALUE) {
                _value as T // Second check inside lock
            } else {

skydoves

// simplified
override val value: T
    get() {
        if (_value === UNINITIALIZED_VALUE) {
            _value = initializer!!()
            initializer = null
        }
        return _value as T
    }