Possible Duplicate:
How do I iterate over each Entry in a Map?
I want to iterate over a TreeMap, and for all keys which have a particular value, I want them to be added to a new TreeMap. How can I do this?
This question is related to
java
collections
treemap
Assuming type TreeMap<String,Integer> :
for(Map.Entry<String,Integer> entry : treeMap.entrySet()) {
String key = entry.getKey();
Integer value = entry.getValue();
System.out.println(key + " => " + value);
}
(key and Value types can be any class of course)
//create TreeMap instance
TreeMap treeMap = new TreeMap();
//add key value pairs to TreeMap
treeMap.put("1","One");
treeMap.put("2","Two");
treeMap.put("3","Three");
/*
get Collection of values contained in TreeMap using
Collection values()
*/
Collection c = treeMap.values();
//obtain an Iterator for Collection
Iterator itr = c.iterator();
//iterate through TreeMap values iterator
while(itr.hasNext())
System.out.println(itr.next());
or:
for (Map.Entry<K,V> entry : treeMap.entrySet()) {
V value = entry.getValue();
K key = entry.getKey();
}
or:
// Use iterator to display the keys and associated values
System.out.println("Map Values Before: ");
Set keys = map.keySet();
for (Iterator i = keys.iterator(); i.hasNext();) {
Integer key = (Integer) i.next();
String value = (String) map.get(key);
System.out.println(key + " = " + value);
}
Using Google Collections, assuming K is your key type:
Maps.filterKeys(treeMap, new Predicate<K>() {
@Override
public boolean apply(K key) {
return false; //return true here if you need the entry to be in your new map
}});
You can use filterEntries instead if you need the value as well.
Just to point out the generic way to iterate over any map:
private <K, V> void iterateOverMap(Map<K, V> map) {
for (Map.Entry<K, V> entry : map.entrySet()) {
System.out.println("key ->" + entry.getKey() + ", value->" + entry.getValue());
}
}
Source: Stackoverflow.com