java 在 HashMap 的 ArrayList 中搜索 HashMap
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Search a HashMap in an ArrayList of HashMap
提问by Ashish Kumar
I have an ArrayList of HashMap. I want to search a HashMap in it but unable to find a way to achieve this. Please suggest me how it can be done? Thanks.
我有一个 HashMap 的 ArrayList。我想在其中搜索 HashMap 但无法找到实现此目的的方法。请建议我怎么做？谢谢。
回答by Lucas Arrefelt
Answer to your question the way i understood it!
按照我的理解回答你的问题！
for (HashMap<String, String> hashMap : yourArrayList)
{
// For each hashmap, iterate over it
for (Map.Entry<String, String> entry : hashMap.entrySet())
{
// Do something with your entrySet, for example get the key.
String sListName = entry.getKey();
}
}
Your Hashmap might use other types, this one uses Strings.
您的 Hashmap 可能使用其他类型，这个使用字符串。
回答by Eduardo Andrade
See if this helps:
看看这是否有帮助：
@Test
public void searchMap() {
List<Map<String, String>> listOfMaps = new ArrayList<Map<String,String>>();
Map<String, String> map1 = new HashMap<String, String>();
map1.put("key1", "value1");
Map<String, String> map2 = new HashMap<String, String>();
map1.put("key2", "value2");
Map<String, String> map3 = new HashMap<String, String>();
map1.put("key3", "value3");
listOfMaps.add(map1);
listOfMaps.add(map2);
listOfMaps.add(map3);
String keyToSearch = "key2";
for (Map<String, String> map : listOfMaps) {
for (String key : map.keySet()) {
if (keyToSearch.equals(key)) {
System.out.println("Found : " + key + " / value : " + map.get(key));
}
}
}
}
Cheers!
干杯!
回答by Salil Pandit
Object myObj;
Object myKey;
//Traverse the list
for(HashMap curMap : listOfMaps){
//If this map has the object, that is the key doesn't return a null object
if( (myObj = curMap.get(myKey)) != null) {
//Stop traversing because we are done
break;
}
}
//Act on the object
if(myObj != null) {
//TODO: Do your logic here
}
If you are looking to get the reference to the Map instead of the object (for whatever reason) same process applies, except you just store the reference to the map:
如果您希望获取对 Map 而不是对象的引用（无论出于何种原因），同样的过程适用，除了您只存储对映射的引用：
Map myMap;
Object myKey;
//Traverse the list
for(HashMap curMap : listOfMaps){
//If this map has the object, that is the key doesn't return a null object
if(curMap.get(myKey) != null) {
//Store instance to the map
myMap = curMap;
//Stop traversing because we are done
break;
}
}
//Act on the map
if(myMap != null) {
//TODO: Do your logic here
}
回答by Pattabi Raman
The Efficient way i've used to search a hashmap in an arraylist without using loops. Since loop makes execution time longer
我用来在不使用循环的情况下在数组列表中搜索哈希图的有效方法。由于循环使执行时间更长
try{
int index = list.indexOf(map); // map is your map to find in ArrayList
if(index>=0){
HashMap<String, String> map = array_list.get(index);
// Here you can get your values
}
}
catch(Exception e){
e.printStackTrace();
Log.i("HashMap","Not Found");
}
回答by Rais Alam
Try below improved code for searching the key in a list of HashMap.
尝试使用以下改进的代码来搜索 HashMap 列表中的键。
public static boolean searchInMap(String keyToSearch)
{
boolean returnVal = false;
List<Map<String, String>> listOfMaps = new ArrayList<Map<String, String>>();
Map<String, String> map1 = new HashMap<String, String>();
map1.put("key1", "value1");
Map<String, String> map2 = new HashMap<String, String>();
map1.put("key2", "value2");
Map<String, String> map3 = new HashMap<String, String>();
map1.put("key3", "value3");
listOfMaps.add(map1);
listOfMaps.add(map2);
listOfMaps.add(map3);
for (Map<String, String> map : listOfMaps)
{
if(map.containsKey(keyToSearch))
{
returnVal =true;
break;
}
}
return returnVal;
}
回答by DeeFour
if you have an ArrayList like this one: ArrayList<HashMap<String, String>>and you want to compare one of the values inside the HashMap try this code.
如果您有这样的 ArrayList：ArrayList<HashMap<String, String>>并且您想比较 HashMap 中的值之一，请尝试此代码。
I use it to compare settings of my alarm notifications.
我用它来比较我的闹钟通知的设置。
for (HashMap<String, String> map : AlarmList) {
for (String key : map.keySet())
{
if (key.equals("SendungsID"))
{
if(map.get(key).equals(alarmMap.get("AlarmID")))
{
//found this value in ArrayList
}
}
}
}
