Java Utililty Methods Map Copy

if (source == null) {
    return null;
final Map<K, V> result = new HashMap<K, V>();
result.putAll(source);
return result;

for (Object k : src.keySet()) {
    Object v = src.get(k);
    dest.put(k, v);

slave.clear();
Iterator itr = master.entrySet().iterator();
while (itr.hasNext()) {
    Map.Entry entry = (Map.Entry) itr.next();
    Object key = entry.getKey();
    Object value = entry.getValue();
    slave.put(key, value);

if (from == null || keys == null)
    return to;
if (to == null)
    to = new HashMap();
for (int i = 0; i < keys.length; i++)
    to.put(keys[i], from.get(keys[i]));
return to;

Map<Object, Object> dst = new HashMap<Object, Object>();
Set<?> entrySet = src.entrySet();
for (Object object : entrySet) {
    if (object != null && object instanceof Entry<?, ?>) {
        Entry<?, ?> entry = (Entry<?, ?>) object;
        Object key = entry.getKey();
        Object value = entry.getValue();
        if (key != null) {
...

Map<K, List<E>> copy = new HashMap<K, List<E>>();
for (Entry<K, List<E>> entry : original.entrySet()) {
    copy.put(entry.getKey(), new ArrayList<E>(entry.getValue()));
return copy;

Map<K, V> copy = new HashMap<>();
for (K key : map.keySet()) {
    copy.put(key, map.get(key));
return copy;

copy.clear();
merge(master, copy);

Map<String, Map<String, String>> copy = new HashMap<>();
if (original != null) {
    for (String key : original.keySet()) {
        copy.put(key, new HashMap<>(original.get(key)));
return copy;

for (Entry<T, K> e : src.entrySet()) {
    dst.put(e.getKey(), e.getValue());