Array merge Sort - Java Collection Framework

Java examples for Collection Framework:Array Sort

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Description

Array merge Sort

Demo Code

/**//  w w w  .  j a  v  a2  s .  c  om
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.Collection;
import java.util.Comparator;

public class Main{
    public static <T> void mergeSort(T[] a, int fromIndex, int toIndex,
            Comparator<? super T> comp) {
        if (toIndex - fromIndex <= 1)
            return;
        getSorter(a, comp).mergeSort(fromIndex, toIndex - 1);
    }
    public static <T> void mergeSort(T[] a, Comparator<? super T> comp) {
        mergeSort(a, 0, a.length, comp);
    }
    public static <T extends Comparable<? super T>> void mergeSort(T[] a,
            int fromIndex, int toIndex) {
        if (toIndex - fromIndex <= 1)
            return;
        getSorter(a).mergeSort(fromIndex, toIndex - 1);
    }
    public static <T extends Comparable<? super T>> void mergeSort(T[] a) {
        mergeSort(a, 0, a.length);
    }
    private static <T> SorterTemplate getSorter(final T[] a,
            final Comparator<? super T> comp) {
        return new SorterTemplate() {
            @Override
            protected void swap(int i, int j) {
                final T o = a[i];
                a[i] = a[j];
                a[j] = o;
            }

            @Override
            protected int compare(int i, int j) {
                return comp.compare(a[i], a[j]);
            }

            @Override
            protected void setPivot(int i) {
                pivot = a[i];
            }

            @Override
            protected int comparePivot(int j) {
                return comp.compare(pivot, a[j]);
            }

            private T pivot;
        };
    }
    private static <T extends Comparable<? super T>> SorterTemplate getSorter(
            final T[] a) {
        return new SorterTemplate() {
            @Override
            protected void swap(int i, int j) {
                final T o = a[i];
                a[i] = a[j];
                a[j] = o;
            }

            @Override
            protected int compare(int i, int j) {
                return a[i].compareTo(a[j]);
            }

            @Override
            protected void setPivot(int i) {
                pivot = a[i];
            }

            @Override
            protected int comparePivot(int j) {
                return pivot.compareTo(a[j]);
            }

            private T pivot;
        };
    }
}

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