Kotlin判断null比较let布尔值Boolean

以你之姓@ 2023-10-15 12:42 0阅读 0赞

### Kotlin判断null比较let布尔值Boolean ###

class MyData {
        val count: Int? = 2023
        val number: Int? = null
    }
    
    fun main(args: Array<String>) {
        val data = MyData()
        val year = 2022
    
        if (data.count != null) {
            if (data.count > year) {
                println("data.count != null")
            }
        }
    
        if (data.count!! > year) {
            println("data.count!!")
        }
    
        var b1 = data.count?.let { it > 2022 } ?: false
        println(b1)
    
        var b2 = data.number?.let { it > 2022 } ?: false
        println(b2)
    
        var b3 = data.count?.let { it > 9999 } ?: false
        println(b3)
    }

> data.count != null  
> data.count!!  
> true  
> false  
> false

[kotlin,null let expression\_zhangphil的博客-CSDN博客当a不为null时,执行大括号里的语句（it肯定不为null）如果a == null ,则为 null。= null，则a.b()如果 a 不是 b，则为 null。当a==null时，执行b。当a不为null时,执行大括号里的语句（it肯定不为null）如果a == null ,则为 null。= null，则a.b()如果 a 不是 b，则为 null。当a==null时，执行b。kotlin的let，with，run，apply，also，异同区别\_zhangphil的博客-CSDN博客。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130538081][kotlin_null let expression_zhangphil_-CSDN_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_kotlin_let_with_run_apply_also_zhangphil_-CSDN_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130538081]

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[kotlin_null let expression_zhangphil_-CSDN_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_kotlin_let_with_run_apply_also_zhangphil_-CSDN_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130538081]: https://blog.csdn.net/zhangphil/article/details/130538081