java - 从 Java 哈希表中的值中检索键

Question

我是 Collection 界的新手，但在我下面的类(class)中，我有哈希表，因为我必须选择哈希表，我想根据值检索关键基础，下面是我的类(class)..

public class KeyFromValueExample
 {
public static void main(String args[]) 
{
Hashtable table = new Hashtable();
        table.put("Sony", "Bravia");
        table.put("Samsung", "Galaxy");
        table.put("Nokia", "Lumia");
System.out.println("does hash table has Lumia as value : " + table.containsValue("Lumia"));
        System.out.println("does hash table Lumia as key : " + table.containsKey("Lumia"));

        //finding key corresponding to value in hashtable - one to one mapping
        String key= null;
        String value="Lumia";
        for(Map.Entry entry: table.entrySet()){
            if(value.equals(entry.getValue())){
                key = entry.getKey();
                break; //breaking because its one to one map
            }
        }
        System.out.println("got key from value in hashtable key:  "+ key +" value: " + value);

//finding key corresponding to value in hashtable - one to many mapping
        table.put("HTC", "Lumia");
        Set keys = new HashSet();

        for(Map.Entry entry: table.entrySet()){
            if(value.equals(entry.getValue())){
                keys.add(entry.getKey()); //no break, looping entire hashtable
            }
        }
        System.out.println("keys : " + keys +" corresponding to value in hash table:  "+ value);

输出:-

does hash table has Lumia as value : true
does hash table has Lumia as key : false
got key from value in hashtable key:  Nokia value: Lumia
keys : [Nokia, HTC] corresponding to value in hash talbe:  Lumia

现在请告知有没有其他更好的方法来实现同样的事情，请告知是否有其他更好的选择。

Answer 1

这看起来很明显它对我做了什么。我不确定是否有更有效的方法，但如果您需要定期查找值以查找键，那么您使用的 map 类型可能是错误的。我建议你把值变成键并制作一个 Map<String, Set<String>>相反