How do I copy or clone a LinkedList-implemented Queue in Java?

Question

I have a Queue q1, that is implemented as a LinkedList, and I want to define a Queue q2, that is a separate, but identical identical instance of Queue q1.

How do I do that since Queue does not implement Cloneable?

Kayaman · Accepted Answer · 2018-03-01T20:53:47.383

28

In a one liner:

new LinkedList<>(myQueue);

Since Queue extends Collection, and collections have a constructor that takes another Collection, this is a quick way to do a shallow clone.

Substitute LinkedList with your own Queue implementation if you wish.

Also, read the javadocs. They have all the answers.

edited Mar 01 '18 at 20:53

answered Apr 10 '14 at 08:08

Kayaman

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new LinkedList(myQueue); should do – nos Apr 10 '14 at 08:11
1

You're right, I'm an idiot. Queue extends Collection. – Kayaman Apr 10 '14 at 08:14

score 5 · Answer 2 · answered Apr 10 '14 at 08:11

5

you can use an iterator :

Iterator<Integer> it = q1.iterator();
while(it.hasNext())  {
   q2.add(it.next());
}

answered Apr 10 '14 at 08:11

mherbert

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score 2 · Answer 3 · answered Apr 10 '14 at 08:09

2

If q1 is one of JCF implementations of Queue like ArrayQueue etc are Cloneable you can use

    Queue q2 = ((Cloneable)q1).clone();

otherwise

    Queue q2 = q1.getClass().newInstance();
    for(Object e : q1) {
        q2.add(e);
    }

answered Apr 10 '14 at 08:09

Evgeniy Dorofeev

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How do I copy or clone a LinkedList-implemented Queue in Java?

3 Answers3