Java Utililty Methods Map Merge

List of utility methods to do Map Merge

  1. HOME
  2. Java
  3. M
  4. Map Merge

Description

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

Method

MapdeepMerge(Map dst, Map src)
Deep merges two maps 
if (dst != null && src != null) {
    for (Object key : src.keySet()) {
        if (src.get(key) instanceof Map && dst.get(key) instanceof Map) {
            Map originalChild = (Map) dst.get(key);
            Map newChild = (Map) src.get(key);
            dst.put(key, deepMerge(originalChild, newChild));
        } else {
            dst.put(key, src.get(key));
...
voiddeepMerge(Map m1, Map m2)
Perform a deep merge of two maps. 
for (K k : m2.keySet()) {
    V v1 = m1.get(k);
    V v2 = m2.get(k);
    if (v1 instanceof Collection && v2 instanceof Collection) {
        if (((Collection<Object>) v1).containsAll((Collection<Object>) v2)) {
        } else {
            ((Collection<Object>) v1).addAll((Collection<Object>) v2);
    } else if (v1 instanceof Map && v2 instanceof Map) {
        deepMerge((Map<Object, Object>) v1, (Map<Object, Object>) v2);
    } else {
        V existingV = m1.get(k);
        if (existingV != null && existingV.equals(v2)) {
        } else {
            m1.put(k, v2);
MapdeepMerge(Map original, Map newMap)
deep Merge 
for (String key : newMap.keySet()) {
    if (newMap.get(key) instanceof Map && original.get(key) instanceof Map) {
        Map<String, Object> originalChild = (Map<String, Object>) original.get(key);
        Map<String, Object> newChild = (Map) newMap.get(key);
        original.put(key, deepMerge(originalChild, newChild));
    } else {
        original.put(key, newMap.get(key));
return original;
Mapmerge(final Map lhs, final Map rhs)
Clones the lhs map and add all things from the rhs map. 
Map<K, V> result = null;
if (lhs == null || lhs.size() == 0) {
    result = copy(rhs);
} else if (rhs == null || rhs.size() == 0) {
    result = copy(lhs);
} else {
    result = copy(lhs);
    result.putAll(rhs);
...
Mapmerge(final Map map1, final Map map2)
merge 
final HashMap<K, V> ret = new HashMap<K, V>(map1);
ret.putAll(map2);
return ret;
HashMapmerge(final Map... maps)
Merges specified maps into one new map and returns it. 
int size = 0;
for (final Map<K, V> map : maps) {
    if (map != null) {
        size += map.size();
final HashMap<K, V> merged = new HashMap<K, V>(size);
for (final Map<K, V> map : maps) {
...
Map>merge(final Map> targetContext, final Map> newContext)
Merge one context onto another by adding or replacing values. 
final HashMap<String, Map<String, String>> result = deepCopy(targetContext);
for (final Map.Entry<String, Map<String, String>> entry : newContext.entrySet()) {
    if (!targetContext.containsKey(entry.getKey())) {
        result.put(entry.getKey(), new HashMap<String, String>());
    } else {
        result.put(entry.getKey(), new HashMap<String, String>(targetContext.get(entry.getKey())));
    result.get(entry.getKey()).putAll(entry.getValue());
...
Mapmerge(List> list)
Merge/combine a list of Map into a single map 
if ((list == null) || (list.isEmpty())) {
    return null;
Map<Character, Long> merged = new HashMap<>();
for (Map<Character, Long> map : list) {
    if ((map == null) || (map.isEmpty())) {
        continue;
    for (Map.Entry<Character, Long> entry : map.entrySet()) {
        char base = entry.getKey();
        Long count = merged.get(base);
        if (count == null) {
            merged.put(base, entry.getValue());
        } else {
            merged.put(base, (count + entry.getValue()));
return merged;
HashMapmerge(Map map1, Map map2)
Creates a new HashMap that has all of the elements of map1 and map2 (on key collision, the latter override the former). 
HashMap retval = new HashMap(calcCapacity(map1.size() + map2.size()));
retval.putAll(map1);
retval.putAll(map2);
return retval;
voidmerge(Map options, Map addition)
merge 
for (Object o : addition.entrySet()) {
    Map.Entry entry = (Map.Entry) o;
    if (entry.getValue() == null)
        options.remove(entry.getKey());
    else
        options.put(entry.getKey(), entry.getValue());