org.glassfish.jersey.internal.guava.Collections2 Maven / Gradle / Ivy

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.glassfish.jersey.internal.guava;

import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Iterator;
import java.util.function.Function;

import static org.glassfish.jersey.internal.guava.Preconditions.checkArgument;
import static org.glassfish.jersey.internal.guava.Preconditions.checkNotNull;

/**
 * Provides static methods for working with {@code Collection} instances.
 *
 * @author Chris Povirk
 * @author Mike Bostock
 * @author Jared Levy
 * @since 2.0 (imported from Google Collections Library)
 */
final class Collections2 {
    static final Joiner STANDARD_JOINER = Joiner.on();

    private Collections2() {
    }

    /**
     * Delegates to {@link Collection#contains}. Returns {@code false} if the
     * {@code contains} method throws a {@code ClassCastException} or
     * {@code NullPointerException}.
     */
    static boolean safeContains(
            Collection collection, Object object) {
        checkNotNull(collection);
        try {
            return collection.contains(object);
        } catch (ClassCastException e) {
            return false;
        } catch (NullPointerException e) {
            return false;
        }
    }

    /**
     * Delegates to {@link Collection#remove}. Returns {@code false} if the
     * {@code remove} method throws a {@code ClassCastException} or
     * {@code NullPointerException}.
     */
    static boolean safeRemove(Collection collection, Object object) {
        checkNotNull(collection);
        try {
            return collection.remove(object);
        } catch (ClassCastException e) {
            return false;
        } catch (NullPointerException e) {
            return false;
        }
    }

    /**
     * Returns a collection that applies {@code function} to each element of
     * {@code fromCollection}. The returned collection is a live view of {@code
     * fromCollection}; changes to one affect the other.
     * 
     * 
The returned collection's {@code add()} and {@code addAll()} methods
     * throw an {@link UnsupportedOperationException}. All other collection
     * methods are supported, as long as {@code fromCollection} supports them.
     * 

     * 
The returned collection isn't threadsafe or serializable, even if
     * {@code fromCollection} is.
     * 

     * 
When a live view is not needed, it may be faster to copy the
     * transformed collection and use the copy.
     * 

     * If the input {@code Collection} is known to be a {@code List}, consider
     * {@link Lists#transform}. If only an {@code Iterable} is available, use
     * {@link Iterables#transform}.
     */
    public static  Collection transform(Collection fromCollection,
                                                 Function function) {
        return new TransformedCollection(fromCollection, function);
    }

    /**
     * Returns best-effort-sized StringBuilder based on the given collection size.
     */
    static StringBuilder newStringBuilderForCollection(int size) {
        CollectPreconditions.checkNonnegative(size, "size");
        return new StringBuilder((int) Math.min(size * 8L, Ints.MAX_POWER_OF_TWO));
    }

    /**
     * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557
     */
    static  Collection cast(Iterable iterable) {
        return (Collection) iterable;
    }

    static class TransformedCollection extends AbstractCollection {
        final Collection fromCollection;
        final Function function;

        TransformedCollection(Collection fromCollection,
                              Function function) {
            this.fromCollection = checkNotNull(fromCollection);
            this.function = checkNotNull(function);
        }

        @Override
        public void clear() {
            fromCollection.clear();
        }

        @Override
        public boolean isEmpty() {
            return fromCollection.isEmpty();
        }

        @Override
        public Iterator iterator() {
            return Iterators.transform(fromCollection.iterator(), function);
        }

        @Override
        public int size() {
            return fromCollection.size();
        }
    }

}