From 7aca97aa2e600bf74266c9e33f9b6470752d19be Mon Sep 17 00:00:00 2001
From: ehlxr <ehlxr.me@gmail.com>
Date: Thu, 15 Jul 2021 21:46:50 +0800
Subject: [PATCH] update at 2021-07-15 21:46:50 by ehlxr

---
 .../io/github/ehlxr/rate/SlideWindow.java     | 107 ++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 src/main/java/io/github/ehlxr/rate/SlideWindow.java

diff --git a/src/main/java/io/github/ehlxr/rate/SlideWindow.java b/src/main/java/io/github/ehlxr/rate/SlideWindow.java
new file mode 100644
index 0000000..1c8b208
--- /dev/null
+++ b/src/main/java/io/github/ehlxr/rate/SlideWindow.java
@@ -0,0 +1,107 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2020 xrv <xrg@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.rate;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+
+/**
+ * 滑动时间窗口限流工具
+ * 本限流工具只适用于单机版，如果想要做全局限流，可以按本程序的思想，用redis的List结构去实现
+ * https://www.cnblogs.com/dijia478/p/13807826.html#!comments
+ *
+ * @author dijia478
+ * @date 2020-10-13 10:53
+ */
+public class SlideWindow {
+    /**
+     * 限制次数
+     */
+    private final int count;
+
+    /**
+     * 时间窗口大小(毫秒)
+     */
+    private final long timeWindow;
+
+    /**
+     * 限流队列
+     */
+    private final List<Long> list;
+
+    public SlideWindow(int count, long timeWindow) {
+        this.count = count;
+        this.timeWindow = timeWindow;
+
+        list = new LinkedList<>();
+    }
+
+    /**
+     * 滑动时间窗口限流算法
+     * 在指定时间窗口，指定限制次数内，是否允许通过
+     *
+     * @return 是否允许通过
+     */
+    public synchronized boolean isGo() {
+        // 获取当前时间
+        long nowTime = System.currentTimeMillis();
+        // 如果队列还没满，则允许通过，并添加当前时间戳到队列开始位置
+        if (list.size() < count) {
+            // 把之前这个位置的数据给依次向后移动
+            list.add(0, nowTime);
+            return true;
+        }
+
+        // 队列已满（达到限制次数），则获取队列中最早添加的时间戳
+        // 用当前时间戳 减去 最早添加的时间戳
+        if (nowTime - list.get(count - 1) <= timeWindow) {
+            // 若结果小于等于timeWindow，则说明在timeWindow内，通过的次数大于count
+            // 不允许通过
+            return false;
+        } else {
+            // 若结果大于timeWindow，则说明在timeWindow内，通过的次数小于等于count
+            // 允许通过，并删除最早添加的时间戳，将当前时间添加到队列开始位置
+            list.remove(count - 1);
+            list.add(0, nowTime);
+            return true;
+        }
+    }
+
+    public static void main(String[] args) throws InterruptedException {
+        SlideWindow slideWindow = new SlideWindow(5, 1000);
+
+        while (true) {
+            // 任意1秒内，只允许5次通过
+            if (slideWindow.isGo()) {
+                System.out.println(System.currentTimeMillis());
+            }
+            // 睡眠0-10ms
+            Thread.sleep(new Random().nextInt(10));
+        }
+
+    }
+
+}
\ No newline at end of file