Main.java Source code

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Here is the source code for Main.java

Source

//package com.java2s;
/*
 * Copyright (C) 2017 FormKiQ Inc.
 *
 * 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.
 */

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

public class Main {
    /**
     * Group Data into {@link List}.
     * @param <T> Type of object
     * @param list {@link List}
     * @param sortBy {@link Comparator}
     * @param groupBy {@link Comparator}
     * @return {@link List}
     */
    public static <T> List<List<T>> groupBy(final List<T> list, final Comparator<T> sortBy,
            final Comparator<T> groupBy) {

        T prev = null;
        List<T> currentlist = new ArrayList<>();
        List<List<T>> results = new ArrayList<>();
        results.add(currentlist);

        List<T> newlist = new ArrayList<>(list);
        Collections.sort(newlist, sortBy);

        Iterator<T> itr = newlist.iterator();
        while (itr.hasNext()) {

            T curr = itr.next();

            if (prev != null) {
                int result = groupBy.compare(curr, prev);

                if (result != 0) {
                    currentlist = new ArrayList<>();
                    results.add(currentlist);
                }
            }

            currentlist.add(curr);

            prev = curr;
        }

        return results;
    }
}