Java限制某段时间内某个请求的次数（代码库）

import com.google.common.cache.Cache;

public class Test2 {
    private static Cache<String, TestObj> guavaCache = CacheFactory.cached(5L, null);
    public static void main(String[] args) {
        guavaCache.put("a", new TestObj());
        guavaCache.put("b", new TestObj());
        for (int i = 0; i < 10; i++) {
            TestObj a = guavaCache.getIfPresent("a");
            if (a == null) {
                System.out.println("a == null");
            } else {
                a.setNum(a.getNum() + 1);
                System.out.println("a == " + a.getNum());
            }

            TestObj b = guavaCache.getIfPresent("b");
            if (b == null) {
                System.out.println("b == null");
            } else {
                b.setNum(b.getNum() + 1);
                System.out.println("b == " + b.getNum());
            }

            if (i == 2) {
                TestObj tmp = new TestObj();
                tmp.setNum(1000);
                guavaCache.put("b", tmp);
            }
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class TestObj {
    private int num = 0;

    public int getNum() {
        return num;
    }

    public void setNum(int num) {
        this.num = num;
    }
}

a == 1
b == 1
a == 2
b == 2
a == 3
b == 3
a == 4
b == 1001
a == 5
b == 1002
a == null
b == 1003
a == null
b == 1004
a == null
b == null
a == null
b == null
a == null
b == null