How to Replace the value in particular key in LinkedHashMap

How to Replace the value in particular key in LinkedHashMap

By : LazyButHappy
Date : November 19 2020, 03:59 PM
like below fixes the issue I want to replace the value in particular key in LinkedHashMap. , You put a new value for that key :
code :

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java cast LinkedHashMap to class extending LinkedHashMap

java cast LinkedHashMap to class extending LinkedHashMap

By : Bilbo Bagosz
Date : March 29 2020, 07:55 AM
it should still fix some issue The problem is that the reference returned simply isn't a reference to an instance of EntireFile. If functionReturningLinkedHashMap just returns a LinkedHashMap, it can't be cast to an EntireFile, because it isn't one - how would it get any extra information about it?
(Judging by your exception, you're actually talking about GroupMap rather than EntireFile, but the same thing applies.)
code :
Object foo = new Object();
String bar = (String) foo; // Bang! Exception
Java LinkedHashMap replace key

Java LinkedHashMap replace key

By : user2325107
Date : March 29 2020, 07:55 AM
I wish this help you If you used the LinkedHashMap, I don't think there is built-in method to achieve your goal. You may want to pick another (or design your own) data-structure.
If you have to do it on a linkedhashmap, you can create a new LinkedHashMap, iterate the old one and put into the new one, when your target entry comes, create a new entry with different key, put the new entry into the map.
How to replace whole key/value pair from a LinkedHashmap at the same replaced position

How to replace whole key/value pair from a LinkedHashmap at the same replaced position

By : Sara
Date : March 29 2020, 07:55 AM
wish of those help As far as I have understood, you want to stick with LinkedHashMap. If you will try to add new data (change the structure of the LinkedHashMap) while iterating over this, you will get ConcurrentModificationException.
Below code might fulfill your requirement :
code :
public static void main(String args[]) throws IOException {

    Map<String, String> testMap = new LinkedHashMap<>();
    testMap.put("1", "One");
    testMap.put("2", "Two");
    testMap.put("3", "Three");
    testMap.put("4", "Four");

    int indexOfFourtyFour = -1;
    System.out.println("Test Map before :: " + testMap);

    Iterator<Entry<String, String>> itr = testMap.entrySet().iterator();
    int index = 0;
    while (itr.hasNext()) {
        Map.Entry<String, String> entry = (Map.Entry<String, String>) itr.next();
        if (entry.getKey().equals("3")) {
            indexOfFourtyFour = index;
        index ++;
    if (indexOfFourtyFour > -1) {
        add(testMap, indexOfFourtyFour, "44", "FourFour");
    System.out.println("Test Map after :: " + testMap);

public static <K, V> void add(Map<K, V> map, int index, K key, V value) {
    assert (map != null);
    assert !map.containsKey(key);
    assert (index >= 0) && (index < map.size());

    int i = 0;
    List<Entry<K, V>> rest = new ArrayList<Entry<K, V>>();
    for (Entry<K, V> entry : map.entrySet()) {
        if (i++ >= index) {
    map.put(key, value);
    for (int j = 0; j < rest.size(); j++) {
        Entry<K, V> entry = rest.get(j);
        map.put(entry.getKey(), entry.getValue());
How to replace HashMap with LinkedhashMap with streams?

How to replace HashMap with LinkedhashMap with streams?

By : Naidu Dokali
Date : March 29 2020, 07:55 AM
will help you You can not avoid collecting the values into the map, before you can create the LinkedHashMap ordered by the resulting values, but you can specify the conversion step as finisher function of your custom collector:
code :
Map<String, Map<String, Long>> organizationApps = input.stream()
    .flatMap(e -> e.entrySet().stream())
    .collect(groupingBy(Map.Entry::getKey, Collector.of(HashMap::new,
        (r, t) -> t.getValue().forEach((k, v) -> r.merge(k, v, Long::sum)),
        (r1, r2) -> {
            r2.forEach((v1, v2) -> r1.merge(v1, v2, Long::sum));
            return r1;
        (Map<String, Long> m) -> m.entrySet().stream()
            .collect(toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2,
Map<String, Map<String, Long>> organizationApps = input.stream()
    .flatMap(m -> m.entrySet().stream())
    .collect(groupingBy(Map.Entry::getKey, collectingAndThen(flatMapping(
            t -> t.getValue().entrySet().stream(),
            toMap(Map.Entry::getKey, Map.Entry::getValue, Long::sum)),
        (Map<String, Long> m) -> m.entrySet().stream()
            .collect(toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2,
How to Replace the value using the old value in particular key in LinkedHashMap in java

How to Replace the value using the old value in particular key in LinkedHashMap in java

By : Sangdragon
Date : March 29 2020, 07:55 AM
To fix the issue you can do I have an old value stored in it as map{key,value}. I want to update the existing value by performing calculations on it like increasing the value by 10 when its an integer; map{key,value+10} , Use computeIfPresent (example assuming a Map):
code :
map.computeIfPresent("key", (String key, Integer value) -> value + 10);
map.merge("key", 1, (Integer oldValue, Integer newValue) -> oldValue + newValue);
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