How can I concatenate two arrays in Java?

To concatenate two arrays in Java, you can use the System.arraycopy method. Here's an example of how you can do this:

int[] a = {1, 2, 3};
int[] b = {4, 5, 6};

int[] c = new int[a.length + b.length];
System.arraycopy(a, 0, c, 0, a.length);
System.arraycopy(b, 0, c, a.length, b.length);

This will create a new array c that contains the elements of a followed by the elements of b.

Alternatively, you can use the Arrays.copyOf method to create a new array that is the combined length of a and b, and then use a loop to copy the elements of a and b into the new array:

int[] a = {1, 2, 3};
int[] b = {4, 5, 6};

int[] c = Arrays.copyOf(a, a.length + b.length);
for (int i = 0; i < b.length; i++) {
  c[a.length + i] = b[i];
}

This will also create a new array c that contains the elements of a followed by the elements of b.

Note that these approaches will create a new array that is the combined length of a and b. They do not modify the original arrays. If you want to modify one of the original arrays, you can use a loop to copy the elements of the other array into it.