org.dizitart.no2.common.util.Iterables Maven / Gradle / Ivy

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/*
 * Copyright (c) 2017-2020. Nitrite author or 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.dizitart.no2.common.util;

import java.lang.reflect.Array;
import java.util.*;

/**
 * @author Anindya Chatterjee.
 * @since 1.0
 */
public class Iterables {
    private Iterables() {}

    public static  T firstOrNull(Iterable iterable) {
        if (iterable == null) return null;

        Iterator iterator = iterable.iterator();
        if (iterator.hasNext()) {
            return iterator.next();
        }
        return null;
    }

    public static  List toList(Iterable iterable) {
        if (iterable instanceof List) return (List) iterable;
        List list = new ArrayList<>();
        for (T item : iterable) {
            list.add(item);
        }
        return list;
    }

    public static  Set toSet(Iterable iterable) {
        if (iterable instanceof Set) return (Set) iterable;
        Set set = new LinkedHashSet<>();
        for (T item : iterable) {
            set.add(item);
        }
        return set;
    }

    @SuppressWarnings("unchecked")
    public static  T[] toArray(Iterable iterable, Class type) {
        T[] dummy = (T[]) Array.newInstance(type, 0);
        if (iterable instanceof Collection) {
            return ((Collection) iterable).toArray(dummy);
        } else {
            List list = new ArrayList<>();
            for (T item : iterable) {
                list.add(item);
            }
            return list.toArray(dummy);
        }
    }

    public static  boolean arrayContains(T[] array, T element) {
        for (T item : array) {
            if (item.equals(element)) return true;
        }
        return false;
    }

    @SafeVarargs
    public static  List listOf(T... items) {
        if (items != null) {
            return Arrays.asList(items);
        }
        return Collections.emptyList();
    }

    @SafeVarargs
    public static  Set setOf(T... items) {
        Set set = new HashSet<>();
        if (items != null) {
            set.addAll(Arrays.asList(items));
        }
        return set;
    }

    public static long size(Iterable iterable) {
        if (iterable instanceof Collection) {
            return ((Collection) iterable).size();
        }

        long count = 0;
        for (Object ignored : iterable) {
            count++;
        }
        return count;
    }

    @SuppressWarnings({"unchecked", "rawtypes"})
    static Object[] toArray(Iterable iterable) {
        if (iterable instanceof Collection) {
            return ((Collection) iterable).toArray();
        } else {
            List list = new ArrayList();
            for (Object item : iterable) {
                list.add(item);
            }
            return list.toArray();
        }
    }
}