限流-令牌桶算法

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * 限流器
 */
public class RateLimiter {
    /**
     * 时间窗口，单位毫秒
     */
    private final long timeWindow;
    /**
     * 窗口时间内最大请求数
     */
    private final int maxRequests;

    private final AtomicInteger requestCount = new AtomicInteger(0);

    private long startTime = System.currentTimeMillis();


    public RateLimiter(int maxRequests, long timeWindow, TimeUnit unit) {
        this.maxRequests = maxRequests;
        this.timeWindow = unit.toMillis(timeWindow);
    }


    /**
     * @return true 继续向下执行，false 阻断执行
     */
    public synchronized boolean tryAcquire() {
        long now = System.currentTimeMillis();
        if (now - startTime > timeWindow) {
            // 重置计数器
            requestCount.set(0);
            startTime = now;
        }
        if (requestCount.incrementAndGet() <= maxRequests) {
            return true;
        } else {
            return false;
        }
    }
}