java实现一个简单的计数器

package com.fengunion.sf;

import org.junit.platform.commons.util.StringUtils;

import java.util.HashMap;
import java.util.Map;
import java.util.Random;

public class CountUtil {
    private static Map<String, Integer> map = null;

    static {
        map = new HashMap<String, Integer>();
    }

    /**
     *
     * 实现一个简单的计数器
     * @param str
     * @return
     */
    public static int countNum(String str) {
        if (StringUtils.isNotBlank(str)) {
            Integer count = map.get(str);
            if (count == null) {
                count = 1;
            } else {
                count++;
            }
            map.put(str, count);
        }
        return map.get(str);
    }

    public static void main(String[] args) {

        for(int i = 0; i<new Random().nextInt(50); i++){
            countNum("a");
        }
        countNum("a");
        countNum("b");
        countNum("b");
        countNum("c");
        int counta = countNum("a");
        int countb = countNum("b");
        countNum("c");
        countNum("c");
        int countc = countNum("c");

        System.out.println(" countaNum: " + counta + " countbNum: " + countb + " countcNum: " + countc);

    }
}