(Java) Array Index out of Bounds?

Question

My code is meant to combine two arrays into one larger array. The two arrays are accepted as arguments into a method, and the method adds the second one to the end of the first one, returning the result. For some reason, I'm getting an arrayIndexOutOfBoundsException. Can someone take a look at this and point out what I'm doing wrong? Thanks.

public static int[] merge(int[] a1, int[] a2) {
    int[] sum = new int[a1.length + a2.length];
    int x;

    for(x = 0; x < a1.length; x++) {
        sum[x] = a1[x];
    }
    for(int k = x; k < sum.length; k++) {
        sum[k] = a2[k];
    }
    return sum;
}

There's a simpler way, see: [Combine to arrays into one](https://stackoverflow.com/questions/80476/how-can-i-concatenate-two-arrays-in-java) — Frakcool, Feb 27 '18 at 22:37
What arrays are you passing to the method? What is your exception method and stacktrace? — Cardinal System, Feb 27 '18 at 22:37
If a1 has 5 elements, and a2 has 1 element, the second for loop will encounter an error when it attempts to dereference a2[k]. — Amir Afghani, Feb 27 '18 at 22:38
You start the second loop not from index 0, i.e. k != 0. Then your sum[k] would be something like sum[x + k]. — iaforek, Feb 27 '18 at 22:41

Antoniossss · Answer 1 · 2018-02-27T22:49:23.500

 for(int k = x; k < sum.length; k++)     sum[k] = a2[k]; // here

sum is larger then a2 so you are getting out of bounds exception

If you wanted to concate 2 arrays it would have to be something like that:

public static int[] merge(int[] a1, int[] a2) {
    int[] sum = new int[a1.length + a2.length];


    for(int x = 0; x < a1.length; x++) {
        sum[x] = a1[x];
    }
    for(int x=0; x < a2.length; x++) {
        sum[a1.length+x] = a2[x];
    }
    return sum;
}

(Java) Array Index out of Bounds?

1 Answers1