211. Add and Search Word - Data structure design

class WordDictionary {

    private WordDictionary[] children=new WordDictionary[26];
    
    boolean isWord=false;
    
    /** Initialize your data structure here. */
    public WordDictionary() {
        
    }
    
    /** Adds a word into the data structure. */
    public void addWord(String word) {
        if(word.length()==0)
        {
            isWord=true;
            return;
        }
        int idx=word.charAt(0)-'a';
        if(children[idx]==null)
            children[idx]=new WordDictionary();
        children[idx].addWord(word.substring(1));
    }
    
    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    public boolean search(String word) {
        if(word.length()==0)
            return isWord;
        if(word.charAt(0)=='.')
        {
            for(int i=0;i<26;i++)
                if(children[i]!=null&&children[i].search(word.substring(1))==true)
                    return true;
            return false;
        }
        else
        {
            int idx=word.charAt(0)-'a';
            if(children[idx]!=null)
                return children[idx].search(word.substring(1));
            return false;
        }
    }
}