Java map traversal mode and performance test
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For the traversal of map in Java, many articles recommend using entryset, which is much more efficient than keyset. The reason is: the entryset method gets the set of all keys and values at one time; The keyset only gets the set of keys. For each key, you need to find an additional value in the map, which reduces the overall efficiency. So what is the actual situation?
<, > map = HashMap<>();
key, value; (i = ; i <= num; i++) { key = + i; value = ; map.put(key, value); } + (i * );
value =
> entry: map.entrySet()) {
key = entry.getKey();
}
> map = TreeMap<
>> iter = map.entrySet().iterator();
(iter.hasNext()) {
key = iter.next().getKey();
}
<> iter = .keySet().iterator();
(iter.hasNext()) {
key = iter.next();
value = .(key); }
( key : .keySet()) {
value =
>> iter = map.entrySet().iterator();
Entry<> entry;
(iter.hasNext()) {
entry = iter.next();
key = entry.getKey();
value = entry.getValue();
}
(Entry<> entry: map.entrySet()) {
key = entry.getKey();
value = entry.getValue();
}
.keySet().iterator();
(iter.hasNext()) {
key = iter.next();
}
.keySet()) {
}
. keySet(). iterator(); (iter.hasNext()) { value = .(iter.next()); }
>> iter = map. entrySet(). iterator(); (iter.hasNext()) { value = iter.next().getValue(); }
> entry: map. entrySet()) { value = entry.getValue(); }
.values().iterator();
(iter.hasNext()) {
value = iter.next();
}
(> entry: map.entrySet()) {
(.(key);