ForkJoin和氣泡排序組合實現的歸併排序

package com.example.demo.studyThread.day4;

import com.example.demo.studyThread.day3.MarkArray;
import com.example.demo.studyThread.day3.SumArray;

import java.util.Random;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;

public class BubbleSort {

    private static int MAX = 100;
    private static int[] meiemi = new int[MAX];

    static {
        Random random = new Random();
        for (int i = 1; i <= MAX; i++) {
            meiemi[i - 1] = random.nextInt(MAX);
        }
    }

    //氣泡排序
    //如果是升序排列的話，每一輪排序找出最大，下一輪都少比較一次
    private static int[] bubbleSort(int[] src){
        for (int i = 0; i < src.length-1; i++) {
            for (int j = 0; j < src.length-i-1; j++) {
                int min;
                if (src[j]>src[j+1]){
                    min = src[j];
                    src[j] = src[j+1];
                    src[j+1]=min;
                }
            }
        }
        return src;
    }

    /**
     * 功能描述 : 將兩個有序陣列合並起來  一次迴圈確認新陣列的一個最小值，放進角標為i的位置
     *
     * @param arr1 陣列1
     * @param arr2 陣列2
     * @return {@link int[]}
     * @author Ziyear 2020-5-21 20:12
     */
    private static int[]  joinInts(int[] arr1, int[] arr2) {
        int left = 0;
        int right = 0;
        int[] mergeArr = new int[arr1.length + arr2.length];
        if (mergeArr.length == 0) {
            return null;
        }
        for (int i = 0; i < arr1.length + arr2.length; i++) {
            if (arr1.length == left) {
                mergeArr[i] = arr2[right];
                right++;
                continue;
            } else if (arr2.length == right) {
                mergeArr[i] = arr1[left];
                left++;
                continue;
            }
            if (arr1[left] <= arr2[right]) {
                mergeArr[i] = arr1[left];
                left++;
            } else {
                mergeArr[i] = arr2[right];
                right++;
            }
        }
        return mergeArr;
    }

    //用forkjoin實現歸併排序
    private static class MergeSortByFoinJoin extends RecursiveTask<int[]>{
        private final static int THRESHOLD = 20;
        private int[] src;
        private int fromIndex;
        private  int toIndex;

        public MergeSortByFoinJoin(int[] src, int fromIndex, int toIndex) {
            this.src = src;
            this.fromIndex = fromIndex;
            this.toIndex = toIndex;
        }

        @Override
        protected int[] compute() {
            if (toIndex-fromIndex<=THRESHOLD){
                return bubbleSort(src);
            }else{
                int mid = (fromIndex+toIndex)/2;
                MergeSortByFoinJoin left = new MergeSortByFoinJoin(src,fromIndex,mid);
                MergeSortByFoinJoin right = new MergeSortByFoinJoin(src,mid+1,toIndex);
                invokeAll(left,right);
                int[] leftjoin = left.join();
                return leftjoin;

            }
        }
    }


    public static void main(String[] args) {
       StringBuilder string = new StringBuilder();
        int[] s = {88,3,73,65,99,108,16,14,19,77,65,98,90,11,80,43};
        for (int i:meiemi
             ) {
            string.append(i+",");
        }
        System.out.println(string);
        System.out.println(
                meiemi.length
        );
        StringBuilder sorts = new StringBuilder();
        ForkJoinPool pool = new ForkJoinPool();
        MergeSortByFoinJoin foinJoin = new MergeSortByFoinJoin(meiemi,0,meiemi.length-1);
        pool.invoke(foinJoin);
        int[] join = foinJoin.join();
        for (int i:join
        ) {
            sorts.append(i+",");
        }
        System.out.println(sorts+"length:"+join.length);
    }
}