Answers for "if key exists in hashmap java"

check if map contains key java

if (map.containsKey(key)) {
       // Okay, there's a key but the value is null
    } else {
       // Definitely no such key
    }

if hashmap contains only one key then how to get that key

HashMap<Node, Integer> x = qu.remove();	
// This "qu" is a queue which is returning a Hashmap
// of type HashMap<Node, Integer> this hashmap contains
// only one key,value pair
Node node = x.keySet().iterator().next();
// here we are extracting that "KEY" of hashMap into variable of Node type