找到了太多答案。有些真的很棒。但我特别在寻找一种方法，这样我就可以用循环得到值。

这就是我最后做的: 对于HashMap 1对1关系:

    Map<String, String> map = new HashMap<String, String>();
    
    map.put("abc", "123");
    map.put("xyz", "456");
    
    for(Entry<String, String> entry : map.entrySet()) {
        if(entry.getValue().equalsIgnoreCase("456")) {
            System.out.println(entry.getKey());
        }
    }

输出:“xyz”

对于HashMap一对多关系:

    Map<String, ArrayList<String>> service = new HashMap<String, ArrayList<String>>();
    
    service.put("abc", new ArrayList<String>());
    service.get("abc").add("a");
    service.get("abc").add("b");
    service.get("abc").add("c");
    
    service.put("xyz", new ArrayList<String>());
    service.get("xyz").add("x");
    service.get("xyz").add("y");
    service.get("xyz").add("z");
    
    for(Entry<String, ArrayList<String>> entry : service.entrySet()) {
        ArrayList<String> values = entry.getValue();
        for(String value : values) {
            if(value.equalsIgnoreCase("x")) {
                System.out.println(entry.getKey());
            }
        }
        
    }

输出:xyz

-谢谢

对于针对API < 19的Android开发，Vitalii Fedorenko一对一关系解决方案无法工作，因为对象。Equals没有实现。这里有一个简单的替代方案:

public <K, V> K getKeyByValue(Map<K, V> map, V value) {
    for (Map.Entry<K, V> entry : map.entrySet()) {
            if (value.equals(entry.getValue())) {
            return entry.getKey();
        }
    }
    return null;
}

/**
 * This method gets the Key for the given Value
 * @param paramName
 * @return
 */
private String getKeyForValueFromMap(String paramName) {
    String keyForValue = null;
    if(paramName!=null)) {
        Set<Entry<String,String>> entrySet = myMap().entrySet();
        if(entrySet!=null && entrySet.size>0) {
            for(Entry<String,String> entry : entrySet) {
                if(entry!=null && paramName.equalsIgnoreCase(entry.getValue())) {
                    keyForValue = entry.getKey();
                }
            }
        }
    }
    return keyForValue;
}

我认为这是最好的解决方案，原始地址:Java2s

    import java.util.HashMap;
    import java.util.Map;

        public class Main {

          public static void main(String[] argv) {
            Map<String, String> map = new HashMap<String, String>();
            map.put("1","one");
            map.put("2","two");
            map.put("3","three");
            map.put("4","four");

            System.out.println(getKeyFromValue(map,"three"));
          }


// hm is the map you are trying to get value from it
          public static Object getKeyFromValue(Map hm, Object value) {
            for (Object o : hm.keySet()) {
              if (hm.get(o).equals(value)) {
                return o;
              }
            }
            return null;
          }
        }

一个简单的用法: 如果你把所有数据放在hasMap中，你有item = "Automobile"，所以你在hashMap中寻找它的键。这是一个很好的解决方案。

getKeyFromValue(hashMap, item);
System.out.println("getKeyFromValue(hashMap, item): "+getKeyFromValue(hashMap, item));

恐怕你只能重复你的地图了。我能想到的最简短的:

Iterator<Map.Entry<String,String>> iter = map.entrySet().iterator();
while (iter.hasNext()) {
    Map.Entry<String,String> entry = iter.next();
    if (entry.getValue().equals(value_you_look_for)) {
        String key_you_look_for = entry.getKey();
    }
}

我认为你的选择是

Use a map implementation built for this, like the BiMap from google collections. Note that the google collections BiMap requires uniqueless of values, as well as keys, but it provides high performance in both directions performance Manually maintain two maps - one for key -> value, and another map for value -> key Iterate through the entrySet() and to find the keys which match the value. This is the slowest method, since it requires iterating through the entire collection, while the other two methods don't require that.