java : Map 사용

Map : 키, value 값 쌍으로 이뤄진 데이터.

HashMap

• put(key, value)
• remove(key)
• get(key)

HashMap<Integer,Integer> map1 = new HashMap<Integer,Integer>();
for(int i =0; i<n; i++){
	if(map1.get(arr[i]) == null){
    	map1.put(arr[i], 1);
    }else{
    	map1.put(arr[i],map1.get(arr[i])+1);
    }
}

TreeMap

• firstEntry()
• firstKey()
• LastEntry()
• LastKey()
• higherEntry(key)
• higherKey(key)
• lowerEntry(key)
• lowerKey(key)