1.语法如下：

fun main(args: Array<String>) {

}

class Person {
    //非静态
    var age = 20
  
   //伴生对象
    companion object {
        //静态
        var name = "张三"
    }
}

2.实现和java一样的单例

fun main(args: Array<String>) {
    println(Person.instance.age)
}

class Person private constructor() {
    //非静态
    var age = 20

    companion object {
        //静态
        var name = "张三"

        val instance by lazy {
            Person()
        }
    }
}

• 惰性加载，只会加载一次，线程安全