About Map Put Versus PutIfAbsent
About Map Put Versus PutIfAbsent
Versus
V put(K key, V value);
意義如下
return map.put(key, value);
V putIfAbsent(K key, V value);
意義如下
if (!map.containsKey(key)) {
return map.put(key, value);
} else {
return map.get(key);
}