com.wrmsr.nativity.util.Maps.java Source code

Introduction

Here is the source code for com.wrmsr.nativity.util.Maps.java

Source

/*
 * 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 com.wrmsr.nativity.util;

import com.google.common.base.Function;
import com.google.common.collect.Lists;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

import static com.google.common.collect.Maps.newHashMap;

public class Maps {
    private Maps() {
    }

    public static <K, E> Map<K, List<E>> buildMapToList(Iterator<E> items, Function<E, K> fn) {
        Map<K, List<E>> map = newHashMap();
        while (items.hasNext()) {
            E item = items.next();
            K key = fn.apply(item);
            List<E> list = map.get(key);
            if (list == null) {
                list = Lists.newArrayList();
                map.put(key, list);
            }
            list.add(item);
        }
        return map;
    }

    public static <K, E> Map<K, List<E>> buildMapToList(Iterable<E> items, Function<E, K> fn) {
        return buildMapToList(items.iterator(), fn);
    }
}