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Move Item in LinkedHashMap


Move Item in LinkedHashMap

By : pasanacm
Date : November 22 2020, 10:33 AM
around this issue It you want to keep the same Map instance, you can do it in 3 lines like this.
code :
Map<Integer, String> map = new LinkedHashMap<>();
map.put(1, "One");
map.put(2, "Two");
map.put(3, "Three");
map.put(4, "Four");

Map<Integer, String> copy = new LinkedHashMap<>(map);
map.keySet().retainAll(Collections.singleton(3));
map.putAll(copy);

System.out.println(map);


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Get next item in LinkedHashMap?

Get next item in LinkedHashMap?


By : Mariya Koleva
Date : March 29 2020, 07:55 AM
This might help you I have the first key/value pair in a LinkedHashMap, which I get from a loop: , Get an iterator and use hasNext() and next():
code :
...
Iterator<Entry<String, String>> it = map.entrySet().iterator();
if (it.hasNext()) {
    Entry<String, String> first = it.next();
    ...
}
...
if (eventHappened && it.hasNext()) {
    Entry<String, String> second = it.next();
    ...
}
...
Get the first item of linkedhashmap

Get the first item of linkedhashmap


By : jeffmlucas
Date : March 29 2020, 07:55 AM
Any of those help I am using LinkedHashMap. I will always process the first value and that can be deleted (if possible) so that during the next iteration I will again take the same first value from the map to process. What can I use to get the first value. , You can use this to get the first element key:
code :
 Object key = linkedHashMap.keySet().iterator().next();
Object value = linkedHashMap.get(key);
linkedHashMap.remove(key);
`ArrayList of HashMap` or `LinkedHashMap` to get item by index

`ArrayList of HashMap` or `LinkedHashMap` to get item by index


By : Daniel Merlo
Date : March 29 2020, 07:55 AM
help you fix your problem I went with experimentating it myself. Turns out the method of creating an ArrayList of HashMaps is about 40 times faster with 1000 elements.
code :
public class HashMapVsArrayOfHashMap {

    public static void main(String[] args){
        ArrayList<HashMap<String, String>> listOfMaps=new ArrayList<HashMap<String,String>>();
        for( int i=0;i<1000;i++){
            final int finalI=i;
        listOfMaps.add(new HashMap<String, String>(){{put("asdfasdfasdfasdfadsf"+finalI,"asdfsdafasdfsadfasdf"+finalI);}});
        }
        LinkedHashMap<String, String> map=new LinkedHashMap<String, String>();
        for(int i=0;i<1000;i++)
            map.put("asdfasdfasdfasdfadsf"+i,"asdfsdafasdfsadfasdf"+i);     
        int position=700;
        testArrayList("Method1:ArrayListOfHashMaps",position,listOfMaps);
        testHashMap("Method2:LinkedHashMap",position,map);
    }

    private static void testArrayList(String string, int position,
            ArrayList<HashMap<String, String>> listOfMaps) {
        long start, end;
        start=System.nanoTime();
        listOfMaps.get(position).get("asdfasdfasdfasdfadsf"+position);
        end=System.nanoTime();
        System.out.println(string+"|Difference = "+(end-start));        
    }
    private static void testHashMap(String string, int position,
            LinkedHashMap<String, String> map) {
        long start, end;
        start=System.nanoTime();

        String s= new ArrayList<String>(map.keySet()).get(position);

        end=System.nanoTime();
        System.out.println(string+"|Difference = "+(end-start));        
    }
}
How do I get the index of an Item in a LinkedHashMap in a List?

How do I get the index of an Item in a LinkedHashMap in a List?


By : user2577262
Date : March 29 2020, 07:55 AM
wish help you to fix your issue I have this Map , You can try this:
code :
 productsNeeded.entrySet().stream()
    .filter(e -> e.getValue()
    .contains(matchingElement))
    .map(Map.Entry::getKey)
    .findFirst();
 productsNeeded.entrySet().stream()
    .filter(e -> e.getValue()
    .contains(matchingElement))
    .map(Map.Entry::getKey)
    .findFirst().orElse(null);
Add item to top of LinkedHashMap

Add item to top of LinkedHashMap


By : Ihor Kanivets
Date : March 29 2020, 07:55 AM
Hope this helps LinkedHashMap retains insertion order.To add it to first you need to iterate through older map and insert values in a new map.
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