In C , when using maps, one of the ways we can quickly create a new entry and update a map at the same time is by simply doing something like:
dict[key] =1;
This allows you to bypass checking to see if a particular key already exists, and then creating an if else statement for it.
I was wondering if there was something similar for Java, especially for a put command.
At present I am stuck using two separate put statements. Trying to use a put statement and combining an addition statement with the value parameter hasn't worked.
CodePudding user response：
Java Map has several related methods, depending on what you need. Probably the most generic method is merge. Your example would translate to:
dict.merge(key, 1, (oldValue, value) -> oldValue value);
There are also a few simpler methods for other purposes, e.g. computeIfAbsent.
CodePudding user response：
Seems it is not possible in the Java world. In c when the key is not present in the map, the key, value pair gets added and its value is by default set to 0 [Default value in map], but in Java when the key is not found it returns null.
But it is possible to bypass the checking by setting the default return value to 0,
int key = 2;
HashMap<Integer,Integer> hm = new HashMap<Integer,Integer>();
hm.put(key, hm.getOrDefault(key, 0) 1);