Why using Arrays.copyof() increased the size of a static array?

Question

I thought Arrays are static, i.e. they cannot be increased or decreased in element size. How come when I declare an array of x elements, I can copy an array of y>x elements into my new array like so:

import java.util.Arrays;

public class CopyOf {

public static void main(String[] args) {
    int[] array ={4,5,4,65,465,4,56,456,6,43,3,5,45};

    //copiedArray has 4 elements
    int[] copiedArray = new int[4];
     copiedArray = Arrays.copyOf(array, array.length);

    // copiedAarray now has 13 elements
    System.out.println(Arrays.toString(copiedArray));

    }

}

Elliott Frisch · Accepted Answer · 2014-11-26 14:22:08Z

9

This

int[] copiedArray = new int[4];

Creates an array reference, and assigns it to a new array with space for 4 int(s). Then, this

copiedArray = Arrays.copyOf(array, array.length);

creates a new array and assigns it to copiedArray. The 4 int(s) created on the previous line are no longer reachable, and are now eligible for garbage collection.

answered Nov 26, 2014 at 14:22

Elliott Frisch

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2 Comments

Crazypigs Over a year ago

I think I understand it better. So copiedArray is pointing to an area in memory assigned for the array. When we use copyOf it is changing the reference address for copiedArray and is assigning it to a new area in memory. The 4int (s) isn't linked to any reference and so cannot be accessed but is still in memory. Is that correct?

Elliott Frisch Over a year ago

@Crazypigs Correct. And since it isn't referenced it can now be garbage collected.

robocoder · Accepted Answer · 2014-11-26 14:35:37Z

3

copiedArray changed its reference from array[4] to array[13]

Now variable array and copiedArray is pointing to the same object.

edited Nov 26, 2014 at 14:35

answered Nov 26, 2014 at 14:21

robocoder

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