util/src/main/java/org/jf/util/ImmutableUtils.java

/*
 * Copyright 2012, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */

package org.jf.util;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

public class ImmutableUtils {
    @Nonnull public static <T> ImmutableList<T> nullToEmptyList(@Nullable ImmutableList<T> list) {
        if (list == null) {
            return ImmutableList.of();
        }
        return list;
    }

    @Nonnull public static <T> ImmutableSet<T> nullToEmptySet(@Nullable ImmutableSet<T> set) {
        if (set == null) {
            return ImmutableSet.of();
        }
        return set;
    }

    @Nonnull public static <T> ImmutableSortedSet<T> nullToEmptySortedSet(@Nullable ImmutableSortedSet<T> set) {
        if (set == null) {
            return ImmutableSortedSet.of();
        }
        return set;
    }
}