Java tutorial
//package com.java2s; import java.util.Collections; import java.util.Set; import javax.annotation.Nullable; public class Main { /** * Returns an non null value based on the giving {@link Set} * * @param set * value to evaluate * @return the original value or an empty {@link Set} * @since 4.2 */ public static <T> Set<T> nonNullSet(@Nullable final Set<T> set) { return set == null ? Collections.emptySet() : set; } }