How to get the first non-null value in Java?

Question

Is there a Java equivalent of SQL's COALESCE function? That is, is there any way to return the first non-null value of several variables?

e.g.

Double a = null;
Double b = 4.4;
Double c = null;

I want to somehow have a statement that will return the first non-null value of a, b, and c - in this case, it would return b, or 4.4. (Something like the sql method - return COALESCE(a,b,c)). I know that I can do it explicitly with something like:

return a != null ? a : (b != null ? b : c)

But I wondered if there was any built-in, accepted function to accomplish this.

Answer 1

No, there isn't.

The closest you can get is:

public static <T> T coalesce(T ...items) {
    for(T i : items) if(i != null) return i;
    return null;
}

For efficient reasons, you can handle the common cases as follows:

public static <T> T coalesce(T a, T b) {
    return a == null ? b : a;
}
public static <T> T coalesce(T a, T b, T c) {
    return a != null ? a : (b != null ? b : c);
}
public static <T> T coalesce(T a, T b, T c, T d) {
    return ...
}

Answer 2

Object COALESCE(Object... objects)
{
    for(Object o : object)
        if(o != null)
            return o;
    return null;
}

Answer 3

Following on from LES2's answer, you can eliminate some repetition in the efficient version, by calling the overloaded function:

public static <T> T coalesce(T a, T b) {
    return a != null ? a : b;
}
public static <T> T coalesce(T a, T b, T c) {
    return a != null ? a : coalesce(b,c);
}
public static <T> T coalesce(T a, T b, T c, T d) {
    return a != null ? a : coalesce(b,c,d);
}
public static <T> T coalesce(T a, T b, T c, T d, T e) {
    return a != null ? a : coalesce(b,c,d,e);
}