From 5831c9bdd36c1e80bb39f686d929e17dd5155dc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BE=90=E6=98=8E=E6=B5=B7?= <173535609@qq.com>
Date: Wed, 17 May 2023 01:11:01 +0800
Subject: [PATCH] java current CopyOnWrite

---
 .../CopyOnWriteArrayListDemo01.java           | 53 +++++++++++++++++++
 .../CopyOnWriteArraySetDemo01.java            | 42 +++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArrayListDemo01.java
 create mode 100644 src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArraySetDemo01.java

diff --git a/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArrayListDemo01.java b/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArrayListDemo01.java
new file mode 100644
index 0000000..0062d8c
--- /dev/null
+++ b/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArrayListDemo01.java
@@ -0,0 +1,53 @@
+package xyz.xuminghai.copy_on_write;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * 2023/5/16 22:30 星期二<br/>
+ * <h1>CopyOnWriteArrayList示例01</h1>
+ * ArrayList的线程安全变体，其中所有可变操作（ add 、 set等）都是通过制作底层数组的新副本来实现的。
+ *
+ * @author xuMingHai
+ */
+public class CopyOnWriteArrayListDemo01 {
+
+    /**
+     * 日志记录器
+     */
+    private static final Logger LOGGER = LoggerFactory.getLogger(CopyOnWriteArrayListDemo01.class);
+
+    /**
+     * 仅在写入时加锁对副本进行修改，最后将修改后的副本替换为原始数组，最终一致性
+     * 适用于对并发时数据的精确度不高，读多写少时使用
+     */
+    private static final CopyOnWriteArrayList<String> COPY_ON_WRITE_ARRAY_LIST =
+            new CopyOnWriteArrayList<>(new String[]{"0", "1", "2", "3", "4"});
+
+
+    public static void main(String[] args) {
+
+        // 多线程并发访问修改
+        new Thread(() -> {
+            LOGGER.info("list = {}", COPY_ON_WRITE_ARRAY_LIST);
+            COPY_ON_WRITE_ARRAY_LIST.set(0, Thread.currentThread().getName());
+            LOGGER.info("list = {}", COPY_ON_WRITE_ARRAY_LIST);
+        }).start();
+
+        new Thread(() -> {
+            LOGGER.info("list = {}", COPY_ON_WRITE_ARRAY_LIST);
+            COPY_ON_WRITE_ARRAY_LIST.set(COPY_ON_WRITE_ARRAY_LIST.size() - 1,
+                    Thread.currentThread().getName());
+            LOGGER.info("list = {}", COPY_ON_WRITE_ARRAY_LIST);
+        }).start();
+
+        // 遍历的只是快照，而不是最新值
+        for (String s : COPY_ON_WRITE_ARRAY_LIST) {
+            LOGGER.info("s = {}", s);
+        }
+
+    }
+
+}
diff --git a/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArraySetDemo01.java b/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArraySetDemo01.java
new file mode 100644
index 0000000..cec3b27
--- /dev/null
+++ b/src/main/java/xyz/xuminghai/copy_on_write/CopyOnWriteArraySetDemo01.java
@@ -0,0 +1,42 @@
+package xyz.xuminghai.copy_on_write;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CopyOnWriteArraySet;
+
+/**
+ * 2023/5/16 22:51 星期二<br/>
+ * <h1>CopyOnWriteArraySet示例01</h1>
+ * 一个使用内部CopyOnWriteArrayList进行所有操作的Set 。因此，它具有相同的基本属性：
+ * 它最适合集合大小通常保持较小、只读操作远远多于可变操作的应用程序，并且您需要防止遍历期间线程之间的干扰。
+ * 它是线程安全的。
+ * 可变操作（ add 、 set 、 remove等）很昂贵，因为它们通常需要复制整个底层数组。
+ * 迭代器不支持可变remove操作。
+ * 通过迭代器遍历速度很快，不会遇到其他线程的干扰。迭代器依赖于在构造迭代器时数组不变的快照。
+ *
+ * @author xuMingHai
+ */
+public class CopyOnWriteArraySetDemo01 {
+
+    /**
+     * 日志记录器
+     */
+    private static final Logger LOGGER = LoggerFactory.getLogger(CopyOnWriteArraySetDemo01.class);
+
+    /**
+     * 实现Set接口的CopyOnWriteArrayList
+     */
+    private static final CopyOnWriteArraySet<String> COPY_ON_WRITE_ARRAY_SET = new CopyOnWriteArraySet<>();
+
+    public static void main(String[] args) {
+        COPY_ON_WRITE_ARRAY_SET.add("1");
+        COPY_ON_WRITE_ARRAY_SET.add("2");
+        COPY_ON_WRITE_ARRAY_SET.add("3");
+        for (int i = 0; i < 2; i++) {
+            COPY_ON_WRITE_ARRAY_SET.add("4");
+        }
+        LOGGER.info("set = {}", COPY_ON_WRITE_ARRAY_SET);
+    }
+
+}