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.
Answer to your question the way i understood it!
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.
See if this helps:
#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!
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:
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
}
Try below improved code for searching the key in a list of HashMap.
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;
}
The Efficient way i've used to search a hashmap in an arraylist without using loops. Since loop makes execution time longer
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");
}
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.
I use it to compare settings of my alarm notifications.
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
}
}
}
}
Related
I set list on another class
List<DataModel> dataList = new ArrayList<DataModel>();
parsed on class
for(DataModel list : dataList) {
final String[] data = {list.getVar_a(), list.getVar_b()};
System.out.println("out data");
System.out.println(list.getVar_a());
System.out.println(list.getVar_b());
}
this prints data
out data
val_a
val_b
Model Class
class DataModel {
private String var_a, var_b;
//Getter & Setter
}
But now, I use and set map on another class and I'm not implementing a model class because in real case it has too many variables.
Map<String, Object> mapData = new LinkedHashMap<String, Object>();
when I set data on map, its result from database
Map<String, Object> map = new LinkedHashMap<String, Object>();
msg = (String) cs.getObject(5);
rs = (ResultSet) cs.getObject(4);
ResultSetMetaData rsmd = rs.getMetaData();
int count = rsmd.getColumnCount();
if(rs.next()){
int jml = 0;
do {
Map<String, Object> data = new LinkedHashMap<>();
for (int i = 1; i <= count; i++ ) {
String name = rsmd.getColumnName(i);
data.put(name, rs.getObject(name));
}
map.put(""+jml, data);
jml++;
} while(rs.next());
setStatus(SUCCESS);
setMessage(msg);
} else {
LOG.info(NO_DATA_FOUND);
}
parsed on class
for(Map.Entry<String,Object> list : mapData.entrySet()) {
String key = list.getKey();
Object val = list.getValue();
System.out.println("out data");
System.out.println(key);
System.out.println(val);
}
this prints data
out data
0
{var_a=val_a, var_b=val_b}
I want to get value on object like this
out data
val_a
val_b
Change your Map for loop to:
for(Map.Entry<String,Object> list : mapData.entrySet()) {
DataModel value = (DataModel) list.getValue();
System.out.println("out data");
System.out.println(value.getVar_a());
System.out.println(value.getVar_b());
}
First you have a map of object, and what you really need is a Map of Map.
Here is your reading a map of object.
for(Map.Entry<String,Object> list : mapData.entrySet()) {
String key = list.getKey();
Object val = list.getValue();
System.out.println("out data");
System.out.println(key);
System.out.println(val);
}
What you really need is a map of map as I am showing below.
Map<String, Map<String, Object>> map = new LinkedHashMap<String, Map<String, Object>>()
Now if you read it as map of map, You can have the result that you need.
0 : {a1:v1, a2:v2, etc...},
1 : {a2:v2, a2:v2, etc...},
2 : {a3:v3, a3:v3, etc...}
for(Map.Entry<String,Map<String, Object> list : mapData.entrySet()) {
String key = list.getKey();
System.out.println("out data");
for(Map.Entry<String,Object> innermap : list.getValue().entrySet()) {
//System.out.println(innermap.getKey());
System.out.println(innermap.getValue());
}
}
I'm trying to iterate the List<Map<String, Object>> and want to check if the code is "approved" or not - if code is having value "approved" then I would like to add "id" as Key and "date" as Value in another hashMap.
List<Map<String, Object>> prodIds = ((List<Map<String, Object>>) myIds.get("result"));
This prodIds returns below set of records:
[{id=[14766724], Date=[1999-01-01]}, {id=[49295837], code=[approved], Date=[2003-04-01]}]
[{id=[58761474621], code=[approved], Date=[2017-09-30]}, {id=[3368781], code=[Cancelled], Date=[2014-01-01]}, {id=[48843224], code=[Cancelled], Date=[2009-01-01]}]
I want the output something like this: If code is "approved" - my new hash map should have value like below:
map.put("49295837", "2003-04-01")
map.put("58761474621", "2017-09-30")
Java Code
List<Map<String, Object>> prodIds = ((List<Map<String, Object>>) myIds.get("result"));
System.out.println("prodIds : " +prodIds );
// [{id=[14766724], Date=[1999-01-01]}, {id=[49295837], code=[approved], Date=[2003-04-01]}]
// [{id=[58761474621], code=[approved], Date=[2017-09-30]}, {id=[3368781], code=[Cancelled], Date=[2014-01-01]}, {id=[48843224], code=[Cancelled], Date=[2009-01-01]}]
Map<String, String> newMap = new HashMap<>();
for (Map<String, Object> map : prodIds) {
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
System.out.println("Key : " +key);
String value = (String) entry.getValue();
System.out.println(" Value : " +value);
}
}
I'm having difficulty how to put the key(id) and value(Date) dynamically if the code value is "approved" into new hash map. It would be really helpful if someone can help me with this.
Appreciated your help in advance!
Thanks
As best as I can determine by your example, this should work. But for each Map<String,Object> I need to know what Object is (e.g. String, List<>, etc).
I am assuming they are lists. If I'm wrong you will get a ClassCastException
public static Map<String, String>
getApproved(List<Map<String, Object>> prodIds) {
Map<String, String> newMap = new HashMap<>();
for (Map<String, Object> map : prodIds) {
if (map.containsKey("code") &&
((List<String>) map.get("code")).get(0)
.equals("approved")) {
newMap.put(((List<String>) map.get("id")).get(0),
(String) ((List<String>) map.get("Date"))
.get(0));
}
}
return newMap;
}
Map<String, String> newMap = getApproved(prodIds);
newMap.entrySet().forEach(System.out::println);
Prints
58761474621=2017-09-30
49295837=2003-04-01
It would help if you could describe all your data structures. Like what is the Object type of map?
I'm putting in a List<Map<String, Object>> the result of a query along with the column names. Sometimes column names are like TableAlias.ColumnName, in that case I want to change it to just ColumnName and remove TableAlias. for that I have below code:
queryResult = namedParameterJdbcTemplateHive.queryForList(query, paramSource);
for (Map<String, Object> map : queryResult) {
for (Map.Entry<String, Object> entry : map.entrySet()) {
String[] keyData = entry.getKey().split("\\.");
if (keyData.length > 0) {
Object obj = map.remove(entry.getKey());
map.put(keyData[1], obj);
}
}
}
That is giving me concurrent modification exception so I was trying with an iterator like below:
for (Map<String, Object> map : queryResult) {
for(Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator(); it.hasNext(); ) {
Map.Entry<String, Object> entry = it.next();
String[] keyData = entry.getKey().split("\\.");
if (keyData.length > 0) {
it.remove();
}
}
}
But not sure how to add the item back with the new key.
Any suggestions please?
I would iterate over the original map and fill another map with the updated keys.
queryResult = namedParameterJdbcTemplateHive.queryForList(query, paramSource);
Map<String, Object> newMap = new HashMap<>();
for (Map.Entry<String, Object> entry : map.entrySet()) {
String[] keyData = entry.getKey().split("\\.");
if (keyData.length > 1) {
newMap.put(keyData[1], entry.getValue());
} else {
newMap.put(entry.getKey(), entry.getValue());
}
}
i have HashMap and its have data,
i connect to database by xmlrpc by jetty9
i am call this function by java client , by this code
Object params[] = new Object[]{stString};
HashMap v1;
v1 = (HashMap<String, Object[]>)server.execute("DBRamService.getRmsValues", params);
i need to print it in my java client , how can i make it ?
this is my function that get data from datebase
HashMap<String, Object[]> result = new HashMap<String, Object[]>();
ArrayList<Double> vaArrL = new ArrayList<Double>();
try {
// i have connected to postgres DB and get data
while (rs.next()){
vaArrL.add(rs.getDouble("va"));
}
int sz = vaArrL.size();
result.put("va", vaArrL.toArray(new Object[sz]));
} catch ( Exception e ) {
System.out.println(e);
e.printStackTrace();
}
return result; }
Following is the snippet to loop through the vArrL and printing the values:
for (int i=0;i<vaArrL.size();i++) {
System.out.println(vaArrL.get(i));
}
Looping through HashMap using Iterator:
Iterator<Entry<String, Object[]>> it = result.entrySet().iterator();
while (it.hasNext()) {
Entry<String, Object[]> pairs = (Entry<String, Object[]>) it.next();
for(Object obj: pairs.getValue()) {
System.out.println(obj);
}
}
Here is how to iterate through a HashMap and get all the keys and values:
// example hash map
HashMap<String, Object[]> v1 = new HashMap<String, Object[]>();
v1.put("hello", new Object[] {"a", "b"});
// print keys and values
for(Map.Entry<String, Object[]> entry : v1.entrySet()) {
System.out.println("Key: " + entry.getKey() + " Values: " + Arrays.asList(entry.getValue()));
}
If you need to print in a different format, you can iterate over the elements of the value array like this:
for(Map.Entry<String, Object[]> entry : v1.entrySet()) {
System.out.println("Key:");
System.out.println(entry.getKey());
System.out.println("Values:");
for (Object valueElement : entry.getValue()) {
System.out.println(valueElement);
}
}
I have ArrayList>. In another activity I want to access all values stored in ArrayList>.
I have tried following code:
ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
for(Hashmap<String, String> map: mylist) {
for(Entry<String, String> mapEntry: map) {
String key = mapEntry.getKey();
String value = mapEntry.getValue();
}
}
but it shows an error at for(Entry<String, String> mapEntry: map) that it only interate over Array.
Your code has bit different for this line,
for(Entry<String, String> mapEntry: map.entrySet())
Try this and let me know what happen,
for (HashMap<String, String> map : mylist)
for (Entry<String, String> mapEntry : map.entrySet())
{
String key = mapEntry.getKey();
String value = mapEntry.getValue();
}
Simple way
Try this i hope it works for u also...
ArrayList<HashMap<String,String>> arraylist;
for (int i=0;i<arraylist.size();i++)
{
HashMap<String, String> hashmap= arraylist.get(i);
String string= hashmap.get("Your_Key_Name");
}
try this
for(HashMap<String,String> map:myList){
for(String str:map.keySet()){
String key=str;
String value=map.get(str);
}
}
Try this instead:
ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
for(HashMap<String, String> map: mylist) {
for(Entry<String, String> mapEntry: map.entrySet()) {
String key = mapEntry.getKey();
String value = mapEntry.getValue();
}
}
Note the line that says for(Entry<String, String> mapEntry: map.entrySet())
According to this thread : Iterate through a HashMap you have to use HashMap.entrySet() method.
You can take a look here too : http://developer.android.com/reference/java/util/HashMap.html