Peter Peter - 1 month ago 9
Java Question

How to remove element from an array

I have an array for example:

String [][] test = {{"a","1"},
{"b","1"},
{"c","1"}};


Can anyone tell me how to remove an element from the array. For example I want to remove item "b", so that the array looks like:

{{"a","1"},
{"c","1"}}


I can't find a way of doing it. What I have found here so far is not working for me :(

Answer

You cannot remove an element from an array. The size of a Java array is determined when the array is allocated, and cannot be changed. The best you can do is:

  • Assign null to the array at the relevant position; e.g.

    test[1] = null;
    

    This leaves you with the problem of dealing with the "holes" in the array where the null values are. (In some cases this is not a problem ... but in most cases it is.)

  • Create a new array with the element removed; e.g.

    String[][] tmp = new String[test.length - 1][];
    int j = 0;
    for (int i = 0; i < test.length; i++) {
        if (j != indexOfItemToRemove) {
            tmp[j++] = test[i];
        }
    }
    test = tmp;
    

    The Apache Commons ArrayUtils class has some static methods that will do this more neatly (e.g. Object[] ArrayUtils.remove(Object[], int), but the fact remains that this approach creates a new array object.

A better approach would be to use a suitable Collection type. For instance, the ArrayList type has a method that allows you to remove the element at a given position.

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