Is there a sorted object list in java?

Question

I have an object with the following memebers:

class XNode {
    // key
    long magicNumber;   

    // metadata:
    int x;
    iny y;
    int z;
    double angle;
    double tempreture;
}

I want to use order list (the key is magicNumber).

Is there a list in java which already implements the add/remove/update in a order manner ? (I dont want to use Collections.sort for every operation).

Short answer, not really, long answer, `TreeSet` "might" help and [this](http://stackoverflow.com/questions/8725387/why-is-there-no-sortedlist-in-java) might shed some more light on it — MadProgrammer, May 29 '15 at 01:14
If you do not need support for duplicates, then `TreeSet` will allow you to iterate in sorted order. However, it doesn't support random access (e.g., the `i`-th element). So whether it will work for you depends on your requirements. You might also take a look at the new [`SortedList`](https://docs.oracle.com/javase/8/javafx/api/javafx/collections/transformation/SortedList.html) of Java FX. — Ted Hopp, May 29 '15 at 01:23

score 3 · Accepted Answer · answered May 29 '15 at 01:25

no duplicates are allowed

First, in XNode there is a typo. I believe

iny y;

should be

int y;

Then you might use a SortedSet (for example TreeSet),

Comparator<XNode> comp = new Comparator<XNode>() {
    @Override
    public int compare(XNode o1, XNode o2) {
        return Long.valueOf(o1.magicNumber).compareTo(o2.magicNumber);
    }
};
SortedSet<XNode> set = new TreeSet<>(comp);

score 2 · Answer 2 · answered May 29 '15 at 01:27

2

Implement Comparable and compare by your magicNumber:

public int compare(XNode other) {
    return Long.compare(this.magicNumber, other.magicNumber);
}

and use a TreeSet.

answered May 29 '15 at 01:27

steffen

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score 2 · Answer 3 · answered May 29 '15 at 01:29

2

There's no sorted list, but you can use a sorted set with a Comparator:

Set<XNode> set = new TreeSet<>((a, b) -> Long.compare(a.magicNumber, b.magicNumber));

This comparator (lambda) distinguishes sorts on magicNumber.

answered May 29 '15 at 01:29

Bohemian

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Is there a sorted object list in java?

3 Answers3