How to create a copy and return its object without using clone?

Question

i was wondering how to create a copy and return its object without using the clone function.

    public double[] Mean(double[][] data) {

    double[] x = data[0].clone();

@PrinceofPersia please answer the question .... also, what do you want to copy, arrays or Object — AxelH, Nov 08 '16 at 10:30
Dear @PrinceofPersia - show a bit of patience. You see, first of all, your question is kinda strange. clone works nicely for the example you provided; so dont push us on providing a solution to a strange question ... — GhostCat, Nov 08 '16 at 10:31
Use this topic hope you can get all details [clonning](http://stackoverflow.com/questions/2156120/java-recommended-solution-for-deep-cloning-copying-an-instance) — FaigB, Nov 08 '16 at 10:33
@PrinceofPersia probably because your question is a bit broad. Don't forget to accept the answer that help you the most. — AxelH, Nov 08 '16 at 10:38
@PrinceofPersia if you think an answer is good, you should accept it (the `v` under the answer score). that way others know the answer works — ItamarG3, Nov 08 '16 at 10:38
@PrinceofPersia wait, I'm confused. Which answer did you choose? it's showing me both of them as accepted [o.o] — ItamarG3, Nov 08 '16 at 10:44
@PrinceofPersia I might add that `Arrays` does it much more efficiently — ItamarG3, Nov 08 '16 at 10:46
@PrinceofPersia you misunderstand me. there's more than one way of doing almost anything in Java, but there are much fewer *right* ways. cloning an object is done via `.clone()` which you didn't want. the second `'right'` way of copying an `array` is using `Arrays.copyOf()`. using a for `loop` is a brute-force method which is less efficient in terms of runtime than `Arrays.copyOf()`... — ItamarG3, Nov 08 '16 at 10:51
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/127620/discussion-between-itamar-green-and-prince-of-persia). — ItamarG3, Nov 08 '16 at 10:53
He wanted to know how it worked. If someone wants to know how to build a car without having the leading expert build it for him you don't give him the address of yet another expert who can build a car for him, you show him how it's done. Sure, brute force is slower, but it's also very simple to understand, which was the point. But honestly this discussion is way off topic, so Prince just choose Itamars as the correct answer, we'll leave the other up too and everyone is happy. — Mark, Nov 08 '16 at 11:32

score 4 · Answer 1 · answered Nov 08 '16 at 10:30

4

You can use this:

double copy = Arrays.copyOf(data[0],data[0].length);

Which will, as the name states, return a copy of the array. NOTE: this will only work for arrays, since it's a method from java.util.Arrays (self-explanatory)

answered Nov 08 '16 at 10:30

ItamarG3

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score 2 · Accepted Answer · answered Nov 08 '16 at 10:30

2

public double[] colMean(double[][] data) {
    double[] x = new double[data[0].length];
    for (int i = 0; i < x.length; i++) {
        x[i] = data[0][i];
    }
    return x;
}

Odd that you only want to copy data[0] though, but whatever...

answered Nov 08 '16 at 10:30

Mark

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Thanks g, this was helpful – Prince of Persia Nov 08 '16 at 10:34
Nice, recreating the wheel but simple – AxelH Nov 08 '16 at 10:37
@AxelH more like an `Array` of wheels ;) – ItamarG3 Nov 08 '16 at 10:39

How to create a copy and return its object without using clone?

2 Answers2