Throwing an UnsupportedOperationException

问题

So one of the method descriptions goes as follows:

public BasicLinkedList addToFront(T data) This operation is invalid for a sorted list. An UnsupportedOperationException will be generated using the message "Invalid operation for sorted list."

My code goes something like this:

public BasicLinkedList<T> addToFront(T data) {
    try {
        throw new UnsupportedOperationException("Invalid operation for sorted list.");
    } catch (java.lang.UnsupportedOperationException e) {
        System.out.println("Invalid operation for sorted list.");
    }
    return this;
}

Is this the right way of doing this? I just printed out the message using println() but is there a different way to generate the message?

回答1:

You don't want to catch the exception in your method - the point is to let callers know that the operation is not supported:

public BasicLinkedList<T> addToFront(T data) {
    throw new UnsupportedOperationException("Invalid operation for sorted list.");
}

回答2:

You could rewrite your code to be like this

public BasicLinkedList<T> addToFront(T data) throws UnsupportedOperationException {
    if (this instanceof SortedList) {
        throw new UnsupportedOperationException("Invalid operation for sorted list.");
    }else{
        return this;
    }
}

That basically accomplishes what you're asking.

来源：https://stackoverflow.com/questions/15329579/throwing-an-unsupportedoperationexception