The title might be misleading because I actually don't know if this piece of code is related to concurrency or not, but I guess it is for the sake of thread safe to some extent...
In openJDK 9 -> TreeMap class -> line 121 and line 370. https://zgrepcode.com/java/openjdk/9/java.base/java/util/TreeMap.java Why does the author need to duplicate a comparator inside the getEntryUsingComparator method instead of referring to the class variable comparator itself?
public class TreeMap<K,V>
extends AbstractMap<K,V>
implements NavigableMap<K,V>, Cloneable, java.io.Serializable
{
private final Comparator<? super K> comparator;
// other code
final Entry<K,V> getEntryUsingComparator(Object key) {
@SuppressWarnings("unchecked")
K k = (K) key;
Comparator<? super K> cpr = comparator; // why duplicate a comparator here?
if (cpr != null) {
Entry<K,V> p = root;
while (p != null) {
int cmp = cpr.compare(k, p.key);
if (cmp < 0)
p = p.left;
else if (cmp > 0)
p = p.right;
else
return p;
}
}
return null;
}
