multidimensional array initialized with array returned by function

Question

I have a problem with the following example:

public static void main(String[] args) {

    // this works
    int[] test1DArray = returnArray();

    int[][] test2DArray = new int[][] {

        // this does not work
        new int[]= returnArray(),

        // yet this does
        new int[] {1, 2 ,3}
}

private static int[] returnArray() {

    int[] a = {1, 2, 3};
    return a;
}

I am looking for a way to create a two-dimensional array, and have the second dimension be the array that is returned from a method. I do not understand why it does not work, as the error I am getting in Eclipse is

The left-hand side of an assignment must be a variable

From my understanding, I am creating a new int array and assigning the returned value to it. Populating the second dimension array immediately like this

new int[] {1, 2 ,3}

works like a charm, and I am looking to do something similar with the array that's returned to me from returnArray()

Any help is greatly appreciated.

p/

Eran · Accepted Answer · 2017-06-05 13:36:27Z

4

Just use:

int[][] test2DArray = new int[][] {
    returnArray(),
    new int[] {1,2 ,3}
};

answered Jun 5, 2017 at 13:36

Eran

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1 Comment

Schlachter Schmidt Over a year ago

Thanks, just what I was looking for!

Robo Mop · Accepted Answer · 2017-06-05 13:43:18Z

2

Although @Eran has solved the problem, I feel you should understand why this went wrong.

When you initialize the contents of an array, you are basically returning values to it.

E.g.: new int[]{1, 2, 3} returns 1, 2, and 3 inside test2Darray, whereas int[] n = new int[]{1, 2, 3} is initializing and declaring an array inside test2Darray. The latter is not returning any primitive value inside the array, so it gives an error.

returnValue() is a method which does return a value (an integer array). So the control considers it equivalent to typing new int[]{1, 2, 3}.

Hence new int[]{1, 2, 3} and returnValue() work.

answered Jun 5, 2017 at 13:43

Robo Mop

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1 Comment

Schlachter Schmidt Over a year ago

Thanks for the background, really helps to understand where I went wrong!

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