安卓Kotlin面试题 41-50

41、如何在 Kotlin 中实现 Builder 模式？

首先，在大多数情况下，您不需要在 Kotlin 中使用构建器，因为我们有默认和命名参数，但如果您需要使用：

//add private constructor if necessary class Car( val model: String?,val year: Int) {         private constructor(builder: Builder) : this(builder.model, builder.year)         class Builder {                 var model: String? = null                 private set                 var year: Int = 0                 private set                 fun model(model: String) = apply {                         this.model = model                  }                 fun year(year: Int) = apply {                         th