将可运行的处理程序升级为lambda表达式

我要升级此代码以使用lambda表达式:

Handler handler = new Handler(Looper.getMainLooper());
handler.postDelayed(new Runnable() {
    @Override
    public void run() {
        missileX = ufoX;
        resetRecent();
        waitForUfoTimer = false;
    }
}, randomize(20000, 18000));

我试着这样做,但它不能编译:

Handler handler2 = new Handler(Looper.getMainLooper());
handler2.postDelayed(Runnable task = () -> {  
    missileX = ufoX;
    resetRecent();
    waitForUfoTimer = false; 
  }
}, randomize(20000, 18000));

哪里有一些指导,让我可以学会怎么做?我必须猜一下语法是荒谬的。