Java UnsupportedOperationException with Collection objects

Question

I have an error using Java Collections in JDK 1.7 : I got this Exception in this line: proposalStatuses.addAll(getAllSubmittedStatuses())

java.lang.UnsupportedOperationException
        at java.util.AbstractList.add(Unknown Source)
        at java.util.AbstractList.add(Unknown Source)
        at java.util.AbstractCollection.addAll(Unknown Source)

trying to add a collection to a list

/**
     * Gets the all submitted statuses.
     *
     * @return the all submitted statuses
     */
    private Collection<ProposalStatus> getAllSubmittedStatuses() {

        return Arrays.asList(
                  ProposalStatus.SAVED_TO_IOS
                , ProposalStatus.SENDED_TO_IOS_IN_PROGRESS
                );
    }

    /**
     * Gets the all received statuses.
     *
     * @return the all received statuses
     */
    private Collection<ProposalStatus> getAllReceivedStatuses() {

        Collection<ProposalStatus> proposalStatuses =

                Arrays.asList(
                  ProposalStatus.RECEIVED_BY_IOS
                , ProposalStatus.SUBMITTED_TO_IOS
                , ProposalStatus.RECEIVED_IOS
                );

        proposalStatuses.addAll(getAllSubmittedStatuses());

        return proposalStatuses;
    }

Answer 1

From the javadoc of Arrays.asList() (emphasis mine):

Returns a fixed-size list backed by the specified array

In short: you cannot .add*() or .remove*() from such a List! You'll have to use another modifiable List implementation (ArrayList for instance).

Answer 2

Arrays.asList() returns an immutable list, that you cannot modify.

More specifically, add(), addAll() and remove() methods are not implemented.