题解 | #计算某字母出现次数#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String line = in.nextLine().toLowerCase();
            String target = in.nextLine().toLowerCase();
            int result = resolve2(line, target);
            System.out.println(result);
        }
    }
    
    public static int resolve1(String line, String target) {
        HashMap<Character, Integer> counter = new HashMap<>();
        for (int i = 0; i < line.length(); ++i) {
            counter.compute(line.charAt(i), (k, v) -> {
                if (v == null) {
                    v = 1;
                } else {
                    v += 1;
                }
                return v;
            });
        }
        return counter.getOrDefault(target.charAt(0), 0);
    }
    
    public static int resolve2(String line, String target) {
        return line.length() - line.replaceAll(target,"").length();
    }
}