I created multi dimensional array using hashmap. How to read value of 2nd array using key which is a String. I read on other articles it say using keyset and iterator but never show how to read specific value using String key.
HashMap<Integer, HashMap<String, String>> myMap = new HashMap<Integer, HashMap<String, String>>();
Example array (structure only):
myMap[1]["title"] = "test";
I can read this:
myMap.get(1);
But i cant read this:
myMap.get(1).get("title");
I also tried but failed:
HashMap<String, String> subHash = myMap.get(position);
subHash.get("title");
Related
If I have a HashMap map that contains values and I want to add those values into an ArrayList, does create copies of those objects when storing them in the ArrayList?
For example, if I do:
ArrayList<String> list = new ArrayList<>();
HashMap<String, String> map = new HashMap<>();
map.put("foo", "bar");
list.add(map.computeIfAbsent("foo", key -> key));
Would adding to the list result in consuming more memory? I read that hashmap fetches value by reference.
ArrayList<Object> parameters = new ArrayList<Object>();
HashMap<String, String> parameter = new HashMap<String, String>();
parameter.put("key", "value");
parameters.add(parameter);
parameters.add((String) "additionalData"); //this line is here for a reason
destinationFunction(parameters);
....
destinationFunction(ArrayList<Object> data){
HashMap<String, String> imported = (HashMap<String, String>) data.get(0);
String value = imported.get("key");
}
How do i achieve this? When i try i receive no errors up until like 2 of destinationFunction where i receive null pointer exception
ArrayList<Object> parameters = new ArrayList<Object>();
relpace this line with what you want to store in array list
like you want to store hash map then create arraylist of type hash map
ArrayList<HashMap<String, String>> parameters = new ArrayList<HashMap<String, String>>();
hope this will help you
Alternative Solution would be using JsonObject and JsonArrays.
they are perfect for such "scenarios" (working with String,Integer and etc with combination of List and Map).
they may also be useful for complex object(e.g. working with Images) but will be abit more difficult to implement. in such cases please refer to java_serialization
in your case use JSONArray instead of your ArrayList and JsonObject instead of HashMap.
use array list of hashmap
ArrayList<HashMap<String, String>>()
Try to put ArrayList<HashMap<String, String>> instead of ArrayList<Object>
create a HashMap and add into the ArrayList.
For Example:-
ArrayList<HashMap<String, String>> list = new ArrayList<>();
HashMap<String, String> map = new HashMap<>();
map.put("KEY", "VALUE");
list.add(map); //Add the map into list
You did not specified what type are you storing in your arrayList. But you assume in your destinationFunction that this list contains only HashMap<String, String> elements. Besides terrible code style it is okay in java to write so. But you made a mistake when put in your arrayList an element of type String which is breaking your assumptions in destinationFunction.
P.S. Try to write more type safe code and avoid generic types with Object type parameter.
I am trying listItem.indexOf(word.text)==-1 to find the string I want.
Using indexOf function in single ArrayList is working fine. but after I use HashMap combine ArrayList, the indexOf function seems not working.
Any solution? thx!
ArrayList<HashMap<String, Object>> listItem= new ArrayList<HashMap<String,Object>>();
SimpleAdapter mSimpleAdapter = new SimpleAdapter(this,listItem, R.layout.item_main, new String[] {"ItemImage","ItemTitle", "ItemText"},
new int[] {R.id.ItemImage,R.id.ItemTitle,R.id.ItemText});
if(listItem.indexOf(word.text)==-1){
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("ItemImage", R.drawable.speak2);
map.put("ItemTitle", word.text);
map.put("ItemText", temp);
listItem.add(map);
}
I'm assuming that word.text is a String. Therefore you have no reason to expect that listItem.indexOf(word.text) would find it in a List that contains HashMap instances.
It looks like you are storing word.text as one of the values of a HashMap stored in the list. To search for a HashMap in the List that contains this value you have to iterate over all the Maps in the List, and for each Map, iterate over all its values.
Perhaps a better data structure would be HashMap<String,HashMap<String, Object>, where the key is taken from word.text and the value is the HashMap you currently store in the list. This way, you could replace listItem.indexOf(word.text) with mapItem.containsKey(word.text), which is more efficient, and would work.
HashMap<String,HashMap<String, Object>> mapItem= new HashMap<String,HashMap<String,Object>>();
if(!mapItem.containsKey(word.text)){
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("ItemImage", R.drawable.speak2);
map.put("ItemTitle", word.text);
map.put("ItemText", temp);
mapItem.put(word.text, map);
}
I'd like to explore the option of using a HashMap to keep track of changes between files. I'm using a few config/text files to give a set of documents of status:
The config file looks like:
STATUS1 = "Doc1.pdf, Doc2.xls, Doc5.doc"
STATUS2 = "Doc8.pdf, Doc6.doc"
STATUS3 = "Doc10.pdf"
...
Instead of having to create a separate HashMap for each instance like so:
Map<String, String> map1 = new HashMap<String, String>();
Map<String, String> map2 = new HashMap<String, String>();
Map<String, String> map3 = new HashMap<String, String>();
map1.put("STATUS1", "Doc1.pdf");
map2.put("STATUS1", "Doc2.xls");
map3.put("STATUS1", "Doc5.doc");
I'd like to have only a single Map with the key of the status and the values mapped to that key.
I don't need help in parsing the file, I just need assistance in implementing the HashMap or Map so I can add this functionality. If there are other datatypes or methods of organizing this data, I'd like to hear your opinions on that.
Any help would be much appreciated.
You can use a MultiMap, which stores multiple values for the same key.
Multimap
Multimap<String, String> myMultimap = ArrayListMultimap.create();
// Adding some key/value
myMultimap.put("STATUS1", "somePDF");
myMultimap.put("STATUS1", "someDOC");
myMultimap.put("STATUS1", "someXCL");
myMultimap.put("STATUS2","someFormat");
// Getting the size
int size = myMultimap.size();
System.out.println(size); // 4
// Getting values
Collection<string> stats1 = myMultimap.get("STATUS1");
System.out.println(stats1); // [somePDF, someDOC, someXCL]
2 . HashMap
With HashMap you can have something like,
List<String> listOfDocs = new ArrayList<String>();
listOfDocs.add("somePDF");
listOfDocs.add("someDOC");
listOfDocs.add("someFormat");
HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
// key would be your STATUS
// Values would be ListOfDocs you need.
map.put("STATUS1", listOfDocs);
map.put("STATUS2", listOfDocs2);
map.put("STATUS3", listOfDocs3);
Hope this helps.
Let me know if you have questions.
I have the following ArrayList
ArrayList<HashMap<String, String>> list;
HashMap<String, String> map;
with the following values inside:
list[0] = map.put("key_0", value_0);
list[1] = map.put("key_1", value_1);
list[2] = map.put("key_2", value_2);
I would like to parse the list array and get the value of the key at a specific position.
You can get the particular map from the ArrayList> by using get() method. for example,
map = list.get(index);
And to get key of that map, you can do:
String key = map.get("key");
FYI, this is the feasible solution, i dont know why you are using key name like key_0, key_1, key_2...and so on.