Question

我有两个ArrayList列表，我要比较它们将它们合并到ArrayList的最终列表中。

示例我有数据库调用，我将这些项目作为

List<List<String>> data1 = dao1.getall();
List<List<String>> data2 = dao2.getall();

data1看起来像

的结果集

"results": [
    [
      "India",
      "Idea",
      "30"
    ],
    [
      "USA",
      "Idea",
      "10"
    ],
    [
      "irland",
      "Idea",
      "10"
    ]

data2看起来像

的结果集

"results": [
    [
      "India",
      "Idea",
      "50"
    ],
    [
      "usa",
      "Idea",
      "30"
    ],
    [
      "sweden",
      "Idea",
      "10"
    ]

我想通过比较Country和Operator字段来合并这两个列表列表，如下所示。

"results": [
    [
      "India",
      "Idea",
      "30",
      "50",
      "80" ====== sum of the above two values
    ],
    [
      "usa",
      "Idea",
      "10",
      "30",
      "40"
    ],
    [
      "irland",
      "Idea",
      "10"
      "0"
      "10"
    ] 
    [
      "sweden",
      "Idea",
      "0"
      "10"       ==== order is very important here 
      "10"
    ]

有人可以帮我吗？提前谢谢。

我试过了，但根本没有为我工作。

  import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;
Public class Hello{
public static void main(String[] args) {
        List<List<String>> list1 = new ArrayList<List<String>>();
        List<List<String>> list2 = new ArrayList<List<String>>();

        // add data

        List<String> datalist1 = new ArrayList<String>();
        datalist1.add("India");
        datalist1.add("vodafone");
        datalist1.add("23");
        list1.add(datalist1);

        System.out.println(list1);
        List<String> datalist2 = new ArrayList<String>();
        datalist2.add("India");
        datalist2.add("vodafone");
        datalist2.add("20");
        list2.add(datalist2);
        System.out.println(list2);

        Collection<List<Country>> list3 = Stream.concat(list1.get(0).stream(), list2.get(0).stream())
                .collect(Collectors.toMap(Country::getCountryName, Country::getOperator, Country::merge)).values();

    }

    private static final class Country {
        private final String countryName;
        private final String operator;
        private final List<String> value;

        public Country(String countryName, String name, List<String> values) {
            this.countryName = countryName;
            this.operator = name;
            this.value = values;
        }

        public String getCountryName() {
            return countryName;
        }

        public String getOperator() {
            return operator;
        }

        public List<String> getValue() {
            return value;
        }

        /*
         * This method is accepting both Country and merging data that you need.
         */
        public static Country merge(Country country1, Country country2) {
            if (country1.getCountryName().equalsIgnoreCase(country2.getCountryName().toLowerCase())
                    && country1.getOperator().equalsIgnoreCase(country2.getOperator().toLowerCase())) {
                List<String> newValue = country1.getValue();
                newValue.add(country2.getValue().get(0));
                Integer Total = Integer.parseInt(country1.getValue().get(0)) + Integer.parseInt(country2.getValue().get(0));
                newValue.add(Total.toString());
                return new Country(country1.getCountryName(), country1.getOperator(), newValue);
            }
            return new Country(country1.getCountryName(), country1.getOperator(), country1.getValue());
        }
    }
    }

Answer 1

如果您使用的是java8，可以在此处使用Map和merge选项。您只需要实现自己的合并方法，它将连接两个元素的数据。

在下面的示例中，我调用了您的班级Country。

@Test
public void should_create_plain_text_tag_for_booking_init_rq() {
    List<Country> data1 = new ArrayList<>();
    List<Country> data2 = new ArrayList<>();

    Collection<Country> results = Stream.concat(data1.stream(), data2.stream())
            .collect(Collectors.toMap(
                    Country::getCountryName, // I asume that you want to merge Data with same country name.
                    Function.identity(),
                    Country::merge)
            ).values();

}

static class Country {
    private final String countryName;
    private final String name;
    private final List<Integer> values;

    public Country(String countryName, String name, List<Integer> values) {
        this.countryName = countryName;
        this.name = name;
        this.values = values;
    }
    /*  This method is accepting both Country and merging data that you need. */
    public static Country merge(Country country1, Country country2) {
        List<Integer> newValue  = country1.getValues();
        newValue.addAll(country2.getValues());
        // compute sum here;
        return new Country(country1.getCountryName(), country1.getName(), newValue);
    }
    // getters
    }

比较并合并java中的两个列表列表，它们生成列表的最终列表

1 个答案: