How to prevent my ToolWindow from been Garbage collected?

I'm new to IntelliJ platform.
I am writing a plugin with a ToolWindow.

When I run my plugin the ToolWindow shows correctly, but it will got GCed and disappear, then the `finalize()` method was called.

```kotlion
class MyToolWindowFactory: ToolWindowFactory, DumbAware {
    override fun createToolWindowContent(project: Project, toolWindow: ToolWindow) {
        val w = MyPanel(toolWindow)
        val contentFactory = ContentFactory.SERVICE.getInstance()
        val content = contentFactory.createContent(w, "", false)
        toolWindow.contentManager.addContent(content)
    }
}

class MyPanel(tw: ToolWindow) : SimpleToolWindowPanel(true, false) {
    private val panel= OnePixelSplitter(false,"My.DetailComponentSplitter", 0.3f)
    private val list = ProblemListView()
    private val detail = ProblemDetailView()
    init {
        panel.firstComponent = list.getComponent()
        panel.secondComponent = detail.getComponent()
        setContent(panel)
    }

    fun finalize() {
        print("")
    }
}
```