I just tried to get add effect with ConcurrentHashMap<String,String>
but the elements order is mixed. Code like a...
ConcurrentHashMap<String,String>h=new ConcurrentHashMap<String,String>();
for(int i=0; i<10; i++)
{
h.put(""+Math.random(), ""+i);
}
Iterator<String> iterator=h.values().iterator();
while(iterator.hasNext())
{
System.out.println(iterator.next());
}
... gives in console next values:
9
4
6
2
0
5
1
7
3
8
... so my question is...
is there a way for ConcurrentHashMap to get original elements order if key is some random string?
Thanks
Use LinkedHashMap
instead it will preserve the order of insertion
Hash table and linked list implementation of the Map interface, with predictable iteration order.
And use
Collections.synchronizedMap(mapInstance)
See Collections.synchronizedMap(mapINstance);
Map<K,V> map = Collections.synchronizedMap(new LinkedHashMap());
LinkedHashMap maintains the order of insertion.
Hash table and linked list implementation of the Map interface, with predictable iteration order. This implementation differs from HashMap in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order). Note that insertion order is not affected if a key is re-inserted into the map.
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