大數組元素差異removeAll與Map效率對比

List<String> listA = new ArrayList<>();
List<String> listB = new ArrayList<>();
//僅在數組A中出現的元素
List<String> onlyListA = new ArrayList<>(listA);
onlyListA.removeAll(listB);
//僅在數組B中出現的元素
List<String> onlyListB = new ArrayList<>(listB);
onlyListB.removeAll(listA);

public class ListDiffTest {
    public static void main(String[] args) {
        testRemoveAllCostTime(1000);
        testRemoveAllCostTime(10000);
        testRemoveAllCostTime(100000);
        testRemoveAllCostTime(1000000);
    }
    public static void testRemoveAllCostTime(int size) {
        List<String> listA = dataList(size);
        listA.add("onlyAElement");
        List<String> listB = dataList(size + 3);
        long startTime = System.currentTimeMillis();
        //僅在數組A中出現的元素
        List<String> onlyListA = new ArrayList<>(listA);
        onlyListA.removeAll(listB);
        //僅在數組B中出現的元素
        List<String> onlyListB = new ArrayList<>(listB);
        onlyListB.removeAll(listA);
        System.out.println("僅在集合A中出現的元素：" + onlyListA);
        System.out.println("僅在集合B中出現的元素：" + onlyListB);
        System.out.println("元素個數 = " + size + "時，比對耗時：" +  (System.currentTimeMillis() - startTime) + " 毫秒");
    }
    private static List<String> dataList(int size) {
        List<String> dataList = new ArrayList<>();
        for (int i = 0; i < size; i++) {
            dataList.add("" + i);
        }
        return dataList;
    }
}

import io.vavr.Tuple2;
public class ListDiffTest {
    public static void main(String[] args) {
        testDifferListByMapCostTime(1000);
        testDifferListByMapCostTime(10000);
        testDifferListByMapCostTime(100000);
        testDifferListByMapCostTime(1000000);
    }
    public static void testDifferListByMapCostTime(int size) {
        List<String> listA = dataList(size);
        listA.add("onlyAElement");
        List<String> listB = dataList(size + 3);
        long startTime = System.currentTimeMillis();
        //僅在數組A中出現的元素
        List<String> onlyListA = tuple2._1;;
        //僅在數組B中出現的元素
        List<String> onlyListB = tuple2._2;
        System.out.println("僅在集合A中出現的元素：" + onlyListA);
        System.out.println("僅在集合B中出現的元素：" + onlyListB);
        System.out.println("元素個數 = " + size + "時，比對耗時：" +  (System.currentTimeMillis() - startTime) + " 毫秒"); 
    }
    /**
     * 通過Map計數方式 比較兩個數組之間的差異
     *
     * @param listA 數組A
     * @param listB 數組B
     * @param <E> 元素類型
     * @return Tuple2對象 onlyAList-隻在數組A存在的元素  onlyBList-隻在數組B存在的元素
     */
    public static <E> Tuple2<List<E>, List<E>> getDiffListBtMapCompare(List<E> listA, List<E> listB) {
        ValidateUtils.validateNotNull(listA, "listA");
        ValidateUtils.validateNotNull(listB, "listB");
        List<E> onlyAList = new ArrayList<>();
        List<E> onlyBList = new ArrayList<>();
        if (CollectionUtils.isEmpty(listA)) {
            return Tuple.of(onlyAList, listB);
        } else if (CollectionUtils.isEmpty(listB)) {
            return Tuple.of(listA, onlyBList);
        }
        /**
         * listA中元素 初始化計數 = 1
         * listB中元素 初始化計數 = -2
         * 遍歷累加後
         * 相同元素 計數 = 2
         * 僅A中出現元素  計數 = 1
         * 僅A中出現元素  計數 = -1
         */
        Map<E, Integer> countMap = new HashMap<>(Math.max(listA.size(), listB.size()));
        for (E eleA : listA) {
            countMap.put(eleA, 1);
        }
        for (E eleB : listB) {
            countMap.put(eleB, 1 + countMap.getOrDefault(eleB, -2));
        }
        countMap.forEach((k, v) -> {
            //獲取不同元素集合
            if (v == 1) {
                onlyAList.add(k);
            } else if (v == -1) {
                onlyBList.add(k);
            }
        });
        return Tuple.of(onlyAList, onlyBList);
    }
}

    public boolean removeAll(Collection<?> c) {
        Objects.requireNonNull(c);
        return batchRemove(c, false);
    }

    private boolean batchRemove(Collection<?> c, boolean complement) {
        final Object[] elementData = this.elementData;
        int r = 0, w = 0;
        boolean modified = false;
        try {
            for (; r < size; r++)
                if (c.contains(elementData[r]) == complement)
                    elementData[w++] = elementData[r];
        } finally {
            // Preserve behavioral compatibility with AbstractCollection,
            // even if c.contains() throws.
            if (r != size) {
                System.arraycopy(elementData, r,
                                 elementData, w,
                                 size - r);
                w += size - r;
            }
            if (w != size) {
                // clear to let GC do its work
                for (int i = w; i < size; i++)
                    elementData[i] = null;
                modCount += size - w;
                size = w;
                modified = true;
            }
        }
        return modified;
    }

    public boolean contains(Object o) {
        return indexOf(o) >= 0;
    }
    public int indexOf(Object o) {
        if (o == null) {
            for (int i = 0; i < size; i++)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = 0; i < size; i++)
                if (o.equals(elementData[i]))
                    return i;
        }
        return -1;
    }