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?
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
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;
}
}
其他回答
可以使用identityHashMap完成,条件是键比较将由==操作符完成,而不是equals()。
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
使用Java收集器
// Group employees by department
Map<Department, List<Employee>> byDept = employees.stream()
.collect(Collectors.groupingBy(Employee::getDepartment));
你的钥匙在哪个部门
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
HashMap<Integer,ArrayList<String>> map = new HashMap<Integer,ArrayList<String>>();
ArrayList<String> list = new ArrayList<String>();
list.add("abc");
list.add("xyz");
map.put(100,list);