Java Utililty Methods Map Invert

List of utility methods to do Map Invert

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Description

The list of methods to do Map Invert are organized into topic(s).

Method

Mapinverse(Map m, Map newMap)
inverse 
for (Entry<K, V> entry : m.entrySet()) {
    newMap.put(entry.getValue(), entry.getKey());
return newMap;
Mapinverse(Map map)
inverse 
Map<V, K> inverse = new HashMap<>(map.size());
for (Entry<K, V> entry : map.entrySet()) {
    if (inverse.put(entry.getValue(), entry.getKey()) != null) {
        throw new IllegalArgumentException(map + " is not a bijection.");
return inverse;
Mapinverse(Map map)
Generates a map with the original map's values as keys and its keys as values. 
Map<V, K> newMap = new HashMap<>(map.size());
for (Map.Entry<K, V> entry : map.entrySet()) {
    if (newMap.containsKey(entry.getValue())) {
        throw new IllegalArgumentException(
                String.format("There are two keys with the value %s in the map", entry.getValue()));
    newMap.put(entry.getValue(), entry.getKey());
return newMap;
CollectioninverseGet(Map map, Object value)
inverse Get 
Collection<K> result = new LinkedList<K>();
for (Iterator<Entry<K, V>> it = map.entrySet().iterator(); it.hasNext();) {
    Entry<K, V> name = it.next();
    if (equalsNullOK(value, name.getValue())) {
        result.add(name.getKey());
return result;
...
Mapinvert(Map map)
Inverts the values of a list. 
Map<B, A> map1 = new HashMap<>();
map.forEach((k, v) -> map1.put(v, k));
return map1;
HashMapinvert(Map in)
invert 
HashMap<V, K> result = new HashMap<V, K>();
for (Map.Entry<K, V> e : in.entrySet()) {
    result.put(e.getValue(), e.getKey());
return result;
Mapinvert(Map map)
Method to invert a map i.e keys becomes values and vice versa 
if (map != null) {
    Map<V, K> returnValue = new HashMap<>();
    for (Entry<K, V> entry : map.entrySet()) {
        if (entry != null) {
            returnValue.put(entry.getValue(), entry.getKey());
    return returnValue;
...
List>invert(Map map, String prefix)
invert 
List<Map<String, Object>> list = new ArrayList<>();
for (Map.Entry<String, Object> entry : map.entrySet()) {
    if (entry.getKey().startsWith(prefix)) {
        String key = entry.getKey().substring(prefix.length());
        if (Iterable.class.isAssignableFrom(entry.getValue().getClass())) {
            int i = 0;
            for (Object e : ((Iterable) entry.getValue())) {
                for (int j = list.size(); j <= i; j++) {
...
Mapinvert(Map map)
invert 
Map<U, T> inversion = new HashMap<U, T>();
for (Entry<T, U> e : map.entrySet()) {
    if (inversion.put(e.getValue(), e.getKey()) != null) {
        throw new IllegalArgumentException("Inversion is not a valid map");
return unmodifiableMap(inversion);
MapinvertedMapFrom(Map source)
Returns a map based on the source but with the key & values swapped. 
Map<V, K> map = new HashMap<>(source.size());
for (Map.Entry<K, V> entry : source.entrySet()) {
    map.put(entry.getValue(), entry.getKey());
return map;