public UserGroup withUserIds(String... userIds) {
        if (this.userIds == null) {
            setUserIds(new com.amazonaws.internal.SdkInternalList<String>(userIds.length));
        }
        for (String ele : userIds) {
            this.userIds.add(ele);
        }
        return this;
    }
<p>
The list of user IDs that belong to the user group.
</p>
<p>
<b>NOTE:</b> This method appends the values to the existing list (if any). Use
{@link #setUserIds(java.util.Collection)} or {@link #withUserIds(java.util.Collection)} if you want to override
the existing values.
</p>

@param userIds
       The list of user IDs that belong to the user group.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-elasticache/src/main/java/com/amazonaws/services/elasticache/model/UserGroup.java