是否有可能实现一个HashMap有一个键和两个值。就像HashMap?

请帮助我,也通过告诉(如果没有办法)任何其他方法来实现三个值的存储与一个作为关键?


当前回答

Apache Commons集合类可以在同一个键下实现多个值。

MultiMap multiMapDemo = new MultiValueMap();

multiMapDemo .put("fruit", "Mango");
multiMapDemo .put("fruit", "Orange");
multiMapDemo.put("fruit", "Blueberry");

System.out.println(multiMapDemo.get("fruit"));

Maven的依赖

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
<dependency>
   <groupId>org.apache.commons</groupId>
   <artifactId>commons-collections4</artifactId>
   <version>4.4</version>
</dependency>

其他回答

不,不只是作为HashMap。你基本上需要一个HashMap,从一个键到一个值的集合。

如果你喜欢使用外部库,Guava在Multimap中就有这个概念,比如ArrayListMultimap, HashMultimap, LinkedHashMultimap等。

Multimap<String, Integer> nameToNumbers = HashMultimap.create();

System.out.println(nameToNumbers.put("Ann", 5)); // true
System.out.println(nameToNumbers.put("Ann", 5)); // false
nameToNumbers.put("Ann", 6);
nameToNumbers.put("Sam", 7);

System.out.println(nameToNumbers.size()); // 3
System.out.println(nameToNumbers.keySet().size()); // 2

我使用Map<KeyType, Object[]>将多个值与Map中的一个键关联起来。这样,我就可以存储与一个键关联的多个不同类型的值。你必须注意保持正确的插入和从Object[]中检索的顺序。

例子: 考虑一下,我们想要存储Student信息。键是id,而我们想要存储姓名,地址和电子邮件与学生相关联。

       //To make entry into Map
        Map<Integer, String[]> studenMap = new HashMap<Integer, String[]>();
        String[] studentInformationArray = new String[]{"name", "address", "email"};
        int studenId = 1;
        studenMap.put(studenId, studentInformationArray);

        //To retrieve values from Map
        String name = studenMap.get(studenId)[1];
        String address = studenMap.get(studenId)[2];
        String email = studenMap.get(studenId)[3];
String key= "services_servicename"

ArrayList<String> data;

for(int i = 0; i lessthen data.size(); i++) {
    HashMap<String, String> servicesNameHashmap = new HashMap<String, String>();
    servicesNameHashmap.put(key,data.get(i).getServiceName());
    mServiceNameArray.add(i,servicesNameHashmap);
}

我得到了最好的成绩。

你只需要创建新的HashMap

HashMap<String, String> servicesNameHashmap = new HashMap<String, String>();

在for循环中。它将具有相同的效果,如相同的键和多个值。

最简单的方法是使用谷歌集合库:

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

public class Test {

    public static void main(final String[] args) {

        // multimap can handle one key with a list of values
        final Multimap<String, String> cars = ArrayListMultimap.create();
        cars.put("Nissan", "Qashqai");
        cars.put("Nissan", "Juke");
        cars.put("Bmw", "M3");
        cars.put("Bmw", "330E");
        cars.put("Bmw", "X6");
        cars.put("Bmw", "X5");

        cars.get("Bmw").forEach(System.out::println);

        // It will print the:
        // M3
        // 330E
        // X6
        // X5
    }

}

Maven链接:https://mvnrepository.com/artifact/com.google.collections/google-collections/1.0-rc2

更多相关信息:http://tomjefferys.blogspot.be/2011/09/multimaps-google-guava.html

我已经习惯了在Objective c中使用数据字典来实现这一目标,而在Java for Android中却很难获得类似的结果。我最终创建了一个自定义类,然后只做了一个自定义类的hashmap。

public class Test1 {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.addview);

//create the datastring
    HashMap<Integer, myClass> hm = new HashMap<Integer, myClass>();
    hm.put(1, new myClass("Car", "Small", 3000));
    hm.put(2, new myClass("Truck", "Large", 4000));
    hm.put(3, new myClass("Motorcycle", "Small", 1000));

//pull the datastring back for a specific item.
//also can edit the data using the set methods.  this just shows getting it for display.
    myClass test1 = hm.get(1);
    String testitem = test1.getItem();
    int testprice = test1.getPrice();
    Log.i("Class Info Example",testitem+Integer.toString(testprice));
}
}

//custom class.  You could make it public to use on several activities, or just include in the activity if using only here
class myClass{
    private String item;
    private String type;
    private int price;

    public myClass(String itm, String ty, int pr){
        this.item = itm;
        this.price = pr;
        this.type = ty;
    }

    public String getItem() {
        return item;
    }

    public void setItem(String item) {
        this.item = item;
    }

    public String getType() {
        return item;
    }

    public void setType(String type) {
        this.type = type;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

}