面试题：使用HashMap统计随机数

1.效果图

2.Java代码

		Random rnd = new Random();
		Map countMap = new HashMap<>();
		for (int i=0; i<1000; i++) {
			int num = rnd.nextInt(4);
			Integer count = countMap.get(num);
			if (count == null) {
				countMap.put(num, 1);
			}else {
				countMap.put(num, count+1);
			}
		}
		for (Map.Entry kv : countMap.entrySet()) {
			System.out.println(kv.getKey() + "," + kv.getValue());
		}