Question

我有两个不同的列表，一个是List<MainCategoriesAPI.Datum> datumList = new ArrayList<>();，第二个是List<SubCategoryEnt> subCategoryEnts1 = new ArrayList<>();。

我想要比较这两个列表，并获取datumList中不存在的ID。然后，我想从SubCategoryEnt中删除有关这些ID的数据。

Answer 1

如果您定位到Android N以上

 List<String> a1 = Arrays.asList("2009-05-18", "2009-05-19", "2009-05-21");
 List<String> a2 = Arrays.asList("2009-05-18", "2009-05-18", "2009-05-19", "2009-05-19", "2009-05-20", "2009-05-21","2009-05-21", "2009-05-22");

 List<String> result = a2.stream().filter(elem -> !a1.contains(elem)).collect(Collectors.toList());

或者您可以使用Collection接口的removeAll方法。

// Create a couple ArrayList objects and populate them
// with some delicious fruits.
Collection firstList = new ArrayList() {{
    add("apple");
    add("orange");
}};

Collection secondList = new ArrayList() {{
    add("apple");
    add("orange");
    add("banana");
    add("strawberry");
}};

// Show the "before" lists
System.out.println("First List: " + firstList);
System.out.println("Second List: " + secondList);

// Remove all elements in firstList from secondList
secondList.removeAll(firstList);

// Show the "after" list
System.out.println("Result: " + secondList);

Answer 2

您必须使用for循环找到相似的ID，然后再次使用for循环从datumList中删除ID；

List<MainCategoriesAPI.Datum> datumList = new ArrayList<>();
List<SubCategoryEnt> subCategoryEnts1 = new ArrayList<>();
List<Integer> results = new ArrayList<Integer>();// this is for storing same ids

获取其他ID

// to get same ids
    if (datumList.size() == subCategoryEnts1.size()) {
        for (int i=0; i<datumList.size();i++){
            int datIds = datumList.get(i);
            for (int j=0; j<subCategoryEnts1.size();j++){
                int subId = subCategoryEnts1.get(j);
                if (datIds!=subId){
                    results.add(subId);
                    break;
                }
            }
        }
    }

删除ID

// to remove same id
        for (int i=0; i<results.size();i++){
            int datIds = results.get(i);
            for (int j=0; j<datumList.size();j++){
                int subId = datumList.get(j);
                if (datIds==subId){
                   datumList.remove(j);
                    break;
                }
            }
        }

希望这会对您有所帮助。

Answer 3

检查以下内容以查找subCategoryEnts1的缺失项

List missingIds = new ArrayList<SubCategoryEnt>();

for (SubCategoryEnt subCategory : subCategoryEnts1) {
    for (MainCategoriesAPI.Datum datam : datumList) {
        if (datam.id == subCategory.id){
            missingIds.add(subCategory);
            break;
        }
    }
}

现在从subCategoryEnts1删除那些

subCategoryEnts1.removeAll(missingIds);

如何比较两个不同的列表并得到两个列表的区别？

3 个答案: