Is there a simpler way to check multiple values against one value in an if-statement?

You can do the following in plain java

Arrays.asList(a, b, c, d).contains(x);

Unfortunately there is no such construct in Java.

It this kind of comparison is frequent in your code, you can implement a small function that will perform the check for you:

public boolean oneOfEquals(int a, int b, int expected) {
    return (a == expected) || (b == expected);
}

Then you could use it like this:

if(oneOfEquals(a, b, 0)) {
    // ...
}

If you don't want to restrict yourselft to integers, you can make the above function generic:

public <T> boolean oneOfEquals(T a, T b, T expected) {
    return a.equals(expected) || b.equals(expected);
}

Note that in this case Java runtime will perform automatic boxing and unboxing for primitive types (like int), which is a performance loss.

As referenced from this answer:

In Java 8+, you might use a Stream and anyMatch. Something like

if (Stream.of(b, c, d).anyMatch(x -> x.equals(a))) {
    // ... do something ...
}

Note that this has the chance of running slower than the other if checks, due to the overhead of wrapping these elements into a stream to begin with.