[JAVA] HashMap

[JAVA] HashMap

-hashmap




메소드 : getOrDefault(Hashmap <key,value>의 value값 ,  초기값 )

리턴값 : 

1. key가 null일 경우 초기값 리턴

2. key가 null이 아닐경우 key 해당하는 value 리턴



ex)  만약 같은 배열(key)이 있을경우 값을 1올린다.

HashMap<String, Integer> hm  = new HashMap<String, Integer>();
String[] book = {"aa","aaaa","bbbb","cccc","aa","bb"}; 

for(String element : book) { 
	hm.put(element, hm.getOrDefault(element, 0)+1); 
}