创建整数域的最快方法是什么？

Question

I have tried to build domain with integer ranges but excluding one point in this range. For example, I should build a range until 4, from always zero. However, I must exclude one point in it say 3. Therefore, my domain should look like array [0,1,2,4]. What is the fastest way to create integer domain?

Answer 1

Create an arraylist of integeres in your domain leaving out one specific element. Something like this:

ArrayList<Integer> domain = new ArrayList<Integer>();    
createDomain(domain, 1, 4, 3);

...
void createDomain(domain, int start, int end, int leaveOutElement) {
    int i;
    for (i = start; i <= end; i++) {
        if (i == leaveOutElement)
            continue;
        domain.add(i);
    }
}

Answer 2

Using Java 8:

final int start = ...;
final int endInclusive = ...;
final int exclude = ...;
int[] domain = IntStream.rangeClosed(start, endInclusive).
        filter(i -> i != exclude).
        toArray();

ie create an IntStream [start, endInclusive] then filter out the value you want to exclude and finally collect it to an array.

As a method:

public int[] createDomain(final int start, final int endInclusive, final int exclude) {
    return IntStream.rangeClosed(start, endInclusive).
            filter(i -> i != exclude).
            toArray();
}