题解 | #统计字符串中字母出现次数# JAVA30

import java.util.ArrayList;
import java.util.Collections;

public class Main {
    public static void main(String[] args) {
        String string = "H e l l o ! n o w c o d e r";
        Scanner scanner= new Scanner(System.in);
        String word = scanner.next();
        scanner.close();
        System.out.println(check(string, word));
    }

    public static int check(String str, String word) {
        //write your code here......
        ArrayList<Character> list = new ArrayList<>();
        for (int i = 0; i < str.length(); i++) {
            list.add(str.charAt(i));
        }
        return Collections.frequency(list, word.charAt(0));
    }
    
    public static int check2(String str, String word) {
        //write your code here......
        int cnt = 0;
        for (int i = 0; i < str.length(); i++) {
            if(str.charAt(i) == word.charAt(0)) {
                cnt++;
            }
        }
        return cnt;
    }
    
    public static int check1(String str, String word) {
        //write your code here......
        int cnt = 0;
        for(int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            String s = new String(ch+"");
            if(s.equals(word)) {
                cnt++;
            }
        }
        return cnt;
    }
}