I'm surprised that neither you nor anyone else has mentioned the fact that the Java 9 "of" functionality won't apply to your example problem. It only goes up to a max of 10 elements, as it simply adds 11 (includes the zero element case) overloads of a static "of" method. It provides no benefit at all really, other than hiding the declaration of 11 ugly methods within the standard library vs one's own code.

As proof, it should be noted that you could add static "of" methods to your builder to get the same Java 9 functionality and also get to your case of 13 elements. For your example, and to be complete, you'd need to add 13 (or 14 with the zero elements case) overloads of "of", which is ugly, but that's all Java 9 does (and again, only to 10 elements). Here's the "of" method for your example:

public static Map of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9, K k10, V v10, K k11, V v11, K k12, V v12, K k13, V v13) {
MapBuilder builder = builder();
builder.put(k1, v1);
builder.put(k2, v2);
builder.put(k3, v3);
builder.put(k4, v4);
builder.put(k5, v5);
builder.put(k6, v6);
builder.put(k7, v7);
builder.put(k8, v8);
builder.put(k9, v9);
builder.put(k10, v10);
builder.put(k11, v11);
builder.put(k12, v12);
builder.put(k13, v13);
return builder.build();
}

private static Map builderPatternWithOf() {
return Maps.of(0, "zero", 1, "one", 2, "two", 3, "three", 4, "four", 5, "five", 6, "six", 7, "seven", 8, "eight", 9, "nine", 10, "ten", 11, "eleven", 12, "twelve");
}

PS: I've moved on to Kotlin. This is a problem I won't ever encounter unless I'm retrofitting old code I haven't yet converted to Kotlin. I highly recommend Kotlin to all. I like Groovy too, but I like Kotlin better.