public static ValueUpdateClassID getID(int id) {
            for (ValueUpdateClassID vucid : ValueUpdateClassID.values()) {
                if (vucid.id == id) {
                    return vucid;
                }
            }
            return null;
        }
Sets the value of this. Ignored by update who have no value
document/src/main/java/com/yahoo/document/update/ValueUpdate.java