非空调用

2021-06-29 13:51:16 +08:00 · 2021-06-29 13:51:16 +08:00 · 90be696c18
commit 90be696c18
parent ed929baed7
1 changed files with 9 additions and 0 deletions
--- a/src/basic/Variable.kt
+++ b/src/basic/Variable.kt
@ -99,4 +99,13 @@ fun main() {
        it == 6L
    }
    println(index)
+
+    // 可空变量
+    var str: String? = null
+    // 安全调用符
+    println(str?.length)
+    // 默认值
+    println(str?.length ?: "默认值")
+    // 非空断言 为空 运行时抛空指针异常
+    println(str!!.length)
 }