diff --git a/builder.kt b/builder.kt
new file mode 100644
index 0000000..8f487ff
--- /dev/null
+++ b/builder.kt
@@ -0,0 +1,22 @@
+data class Hoge(
+  val id:Int,
+  val name:String) {
+  class HogeBuilder() {
+    var id:Int? = null
+    var name:String? = null
+    fun build() : Hoge = Hoge(
+       id = requireNotNull(id),
+       name = requireNotNull(name)
+     )
+   }
+}
+
+fun main(args: Array<String>) {
+  var builder = Hoge.HogeBuilder()
+  builder.id = 1
+  builder.name = "hoge"
+  var e:Hoge = builder.build()
+
+  println(e.id)
+  println(e.name)
+}