leetcode No.383赎金信

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        HashMap<Character,Integer> magMap=new HashMap<>();
        char[] mag=magazine.toCharArray();
        for(char c:mag){
            if(!magMap.containsKey(c))
                magMap.put(c,1);
            else magMap.put(c,magMap.get(c)+1);
        }
        char[] ransom=ransomNote.toCharArray();
        for(char c:ransom){
            if(magMap.getOrDefault(c,0)==0)
                return false;
            else magMap.put(c,magMap.get(c)-1);
        }
        return true;
    }
}