Notify observers when list elements changed

ObservableList.kt

import java.util.*

class ObservableList<T>(private val wrapped: MutableList<T>): MutableList<T> by wrapped, Observable() {
    override fun add(element: T): Boolean {
        if (wrapped.add(element)) {
            setChanged()
            notifyObservers()
            return true
        }
        return false
    }

    override fun addAll(elements: Collection<T>): Boolean {
        if (wrapped.addAll(elements)){
            setChanged()
            notifyObservers()
            return true
        }
        return false
    }

    override fun clear() {
        wrapped.clear()
        setChanged()
        notifyObservers()
    }

    override fun remove(element: T): Boolean {
        if (wrapped.remove(element)){
            setChanged()
            notifyObservers()
            return true
        }
        return false
    }
    
    
    override fun removeAt(index: Int): T {
        setChanged()
        notifyObservers()
        return wrapped.removeAt(index)
    }

    override fun removeAll(elements: Collection<T>): Boolean {
        if (wrapped.removeAll(elements)){
            setChanged()
            notifyObservers()
            return true
        }
        return false
    }
}